Science clashes with science in this swiftly moving tale, crowded with breathless action. Try to identify the man in the black mask!

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WHEN will the world realize that guns and bombs as weapons of murder are being superseded by instruments twice as deadly, and ten times as difficult to defend oneself against?

We read in the daily press, that scientists have proved the theory of atomic destruction of matter. Yet only a few years ago, science teachers taught us that matter was indestructible. Do we realize that each new accomplishment of science, besides helping mankind, also gives the educated criminal a new armory to war against unprotected civilization? And that, in order to combat these new perils, science must come to the aid of the detective, guiding and assisting him in the detection of crime, and the conviction o the criminal?

Radium, for instance! A boon to the sick, yet at the same time, a terrible menace in the hands of an evildoer. In this story Mr. Curry, who is a writer too well known to need introduction to our readers, develops an extraordinary plot, full of sound, practical and every-day science.

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RAYS OF DEATH

By Tom Curry

CHAPTER I
Lawson Is Called Back

DETECTIVE MORAN'S steel-grey eyes looked straight ahead as he climbed the flight of stairs which led to the lighted door. Various odors, strange to him and lumped by the detective under the descriptive name of "stinks", reached his nostrils. He squared his broad shoulders and took the derby from his bullet head, displaying short-clipped brown hair.

"Lawson!" he called.

"Here! Is that you, Moran?"

Young Lawson, a research chemist who had formerly been a member of the police organization, but was now working for a private company, held out a hand stained yellow and brown by chemicals and sat his visitor down in a nearby chair.

"Gosh, Lawson!" exclaimed the detective. "We surely miss you. Too bad the red tape put you out."

It was red tape alone which had caused the department to oust Lawson. The great chemist had been working at a small salary, but with unlimited facilities, in his own laboratory in police headquarters. But, since he had no regular duties but simply came and Went as he pleased, the ire of some hard-boiled official was aroused, and he had been discharged. The work of the department was done by city chemists and doctors; liquor analyses, forensic medicine and bacteriology being outside of the realm of the common detective. The inspector who had brought the valuable Lawson into the organization, and allowed him free run of the city's facilities, had been reprimanded.

Moran admired the quality of Lawson's mind too much to allow the chemist to drop out of his busy life. He visited Lawson whenever possible and, though the chemist was often irritable and refused to be disturbed while he was working, Moran did not take it amiss. He knew Lawson liked him.

The scientist was pale, with an acid scar under his right eye; a slender man, with delicate, long fingers and light blue eyes. His head was large, and his brown hair in a state of perpetual disorder.

"I've come on business," said Moran delicately: "I know we have no call on you any more, Lawson—it was a dirty trick to let you out that way—but I thought, if you weren't too busy—"

Moran stopped, evidently embarrassed. Lawson laughed: "Go on, Moran! You know I don't care about that. I had a good time while I was with you and enjoyed the work we did together. While I wouldn't care to be bothered here by most of your colleagues—I'm too busy for that-you're welcome to come and take a chance any time if I can be of assistance and can spare the time."

"Yes, I thought you'd feel that way. I'm out of my depth now, and I hate to admit it to the chief. You know, when you were helping me, I solved two or three chemical cases. That's why they put me on this one."

"What's happened, then? A poisoning?"

The detective's brow corrugated in thick lines:

"No. It might almost be an accident. I've been out there all day. Was put on special detail. The local police are working on it, but headquarters sent me to see what I could do. Have you ever heard of radium?"

Lawson laughed: "I should say so!"

"I mean, do you know much about it? Is it inflammable?"

"Scarcely that. It burns itself up. The chemistry of the radium elements is magnificent, Moran. You see, the metal is decomposing itself, but the action cannot be hurried or retarded. Radium salts—the metal itself is scarcely known—give off three rays: the alpha ray, which consists of positively charged helium¹—that's used in dirigibles now instead of hydrogen; the beta rays, negatively-charged electrons or units of electricity; and the gamma rays, which are very similar to X-rays. The alpha rays will illuminate a zinc-sulphide screen—which is how we make our luminous watch and clock dials. In 1898—"

1: Helium is one of the elements first discovered in other planets or stars. As early as 1868, the presence and existence of helium was discovered in the sun by spectroscopic examination of the suns light. It is to this fact it owes its name; helios being the Greek word meaning sun. Its atomic weight is 4.0, as compared to hydrogens 1.008: but its lower efficiency as a for dirigibles is offset by non-inflammableness. It was finally isolated by Ramsey in 1895.

"Cut it out!" begged Moran, mopping his brow: "I'll talk and you can figure it out in your own head. Do you read the papers?"

A Curious Explosion

LAWSON shook his head: "Not every day. I've been up here now for three days and haven't been out. My food is brought in to me and I take a nap on the couch once in a while. Why?"

"Because you must have seen the account of the terrific explosion. The Malloradium Company's plant blew up like a leaky still at two A. M. Monday night, and the whole building was demolished. Luckily, the plant stands off by itself in a large field, or there would have been a lot more damage done. The fire has been extinguished after a hard fight. Two watchmen inside were killed, and two who were patrolling the grounds were knocked for a goal. They're able to talk now, and I had a word with them. Do you know what they say?"

"No. Moran, you seem excited?"

"Sure I am. The watchmen say they couldn't see well Monday night because of the fog!" Lawson, smoking a cigaret, watched his friend's face. Moran half smiled, half frowned: "Listen, Lawson. There was no fog on Monday night! It was clear, moonlight, stars shining as pretty as could be. Everybody in the neighborhood says the same thing."

"Maybe the watchmen were raving."

"No. They both claim the same thing. Whoever blew up the plant—and no doubt it was blown up—got in under cover of the fog and entered the building. The two watchmen inside were taken care of, bound and left to be blown to hell. We found some parts of the poor fellows."

"But where does the radium come in?"

"I'll tell you something about the company. There's a man named William Keating out there, almost crazy, picking over the ruins. He thinks the explosion might have been accidental, spontaneous combustion or something like that, and that his precious radium may be lying in there somewhere. There was an ounce of the stuff in the company's safe, in the basement. Well, this Keating has been trying to dig out the safe and has got burned and made himself a nuisance to the firemen. The owner of the works, Byfield Mallory, has been out there, too, raging around. D' you know how much he says that little bit of white powder is worth?"

"About two million dollars," said Lawson, after' a rapid calculation: "Radium's selling at $70,000 a gram—or was, the last time I heard. But I thought the Belge concern had a monopoly on the stuff? Didn't know the Americans were making any just now."

"I couldn't tell you about that. But two million dollars for a few pinches of stuff seems like a Chinaman's dream to me. Could it be true?"

"Surely. It takes some nine hundred processes to get a few milligrams of radium out of several tons of uranium ore, either pitchblende or carnotite. Pitchblende is found in Europe, the carnotite found in the American West."

Moran held up his hands: "You can see how I feel. Keating and Mallory are just about crazy, and I can't get much out of them. Keating won't believe the radium actually is stolen. He keeps saying no one could sell it without being caught."

"That's true. Anybody who turned up with an ounce of radium would be investigated at once. Only hospitals, research laboratories and, perhaps, a few factories which manufacture such things as airplane struts or luminous dials could have any use for radium. Doctors usually borrow it from radium banks."

"Well—I hate to quit on this case. It would be a feather in my cap if I could find that radium. I've got men searching the ruins now; but the fog the watchmen mention made me wonder if there wasn't something more to it than there seems to be. By the way—the experts claim that the explosion looks like T.N.T. had been used."

"Trinitrotoluol?² Possibly. Now, I'm working on something, but am at a phase where I can leave it for a few days. I'll meet you here tomorrow morning, and we'll go out and take a look. Where's the factory—-or what's left of it?"

2: Trinitotoluol (or toluene). A high explosive made by treating toluene with nitric acid—thus forming the chemical compound CH₃C₆H₂ (NO₂)₃. This substance, generally referred to as T.N.T., is used for filling high explosive shells: for it melts readily (at 81.5° Centigrade) and can be poured from one vessel to another rapidly and in safety.

"Out in Queens. As I told you, Mallory owns a tract of flat land out there, and it was there the radium plant was built."

"All right, then. I'll see you tomorrow. S'long."

Moran took his leave, to go home and snatch a few hours sleep. Hope was in his heart, hope that he might be the one to solve the case. He had been assigned to it on special detail, and wished to keep his reputation clear as a solver of chemical mysteries. In this, Lawson was his chief aid. Moran would place the facilities of the great organization at the chemist's call, and Lawson would direct the inquiry through the detective.

CHAPTER II
$2,000,000.00 GONE

THE spring sun shone brightly, as Detective Moran, escorting his friend Lawson, stepped up to the wire gate of what had been the Malloradium Company's plant. A railroad switch ran in from the nearby main line; and two or three cars, which had come from the West with the carnotite ore from which the radium was extracted, were lying as they had fallen from the force of the explosion.

Piles of brick, plaster, and burned material, vats, furnaces and broken glassware were strewn about in profusion. The amount of labor necessary to obtain the radium was so immense, and the chemicals so numerous, that it was actually cheaper to transport the heavy ore from the West than to take the chemicals to the uranium deposits. To produce a single gram of radium bromide, five hundred tons of ore had to be treated with some five hundred tons of chemicals and a Niagara of distilled water.

Moran was admitted at once, Lawson trailing after him. Firemen and police stood about; and inside the inclosure were several cars, among them a black limousine.

"That car belongs to Mallory, the owner," said Moran, indicating the limousine: "There he is, himself, over by those tubs. That's Keating with him, the smaller fellow."

Lawson looked at them. Mallory, the owner of the demolished factory, was a huge, bluff man, with iron-gray hair and a red face. The chemist, watching him, could see the temper which Mallory was venting on his manager. Keating, black of hair, was of slighter build; just now he wore a worried look.

The detective and his friend made their way past the cars towards the group by the ruins. As Lawson, picking his way among the bits of brick and wood which had been placed there by the terrible hand of the explosion, passed the limousine, he glanced up.

The chauffeur was on the seat, but Lawson did not look at the driver. He caught sight of the white face of a girl who was staring at the ruins.

She was beautiful. Her face, though pale, was exquisite in appearance, and her great dark eyes lighted her countenance. She was slight of figure, but clothed with a simplicity which was elegant. Lawson, whose heart had began to leap, stopped beside the car. He saw dark curls under her small hat.

For a moment, the chemist, usually so businesslike, stared at the girl with what might have been rudeness, had it not been for the honest admiration in his gaze.

Moran had gone on. He was talking, thinking Lawson was still at his side. The girl, seeing the detective speaking to empty air, looked round and caught sight of the chemist, struck dumb by her beauty. For a moment, a surprised little smile appeared on her red lips; then she flushed and turned away.

The detective discovered Lawson's absence, and turned to see where the chemist was. But Lawson was already running after him.

They stopped for a few: moments at the edge of the ruins.

"Some job, eh?" said Moran, almost proudly. Keating, the manager, perceiving Moran, hurried over to him.

"Mr. Mallory's here," he said: "I've been hoping against hope to find the radium in the vault. But the vault has been smashed, too. The men have just reached it. Thirty grams of it-imagine! Worth over two million dollars."

Moran strode over to where the big bluff owner of the works stood frowning at the debris. Mallory gave the detective but a short nod, and then turned on Keating, as the manager returned to his side. Lawson was at his heels.

"What about the bank at the new hospital, eh?" roared Mallory. "Where's my $100,000 guarantee that I'll have the stuff delivered, purified, ready for use, next Wednesday?"

"Mr. Mallory, it must be in there somewhere! The safe is on its face; it looks smashed, but once we get it turned over, we may find the radium. I've sent for more tools. Let's hope it's there."

"And suppose it isn't?" growled Mallory: "What a fool you are, Keating! You may be a good chemist, but you're a rotten executive."

Keating hung his head: "If the worse comes to the worst, sir," he said, "we can get ten grams of radium chloride, enough to fill the hospital order, from Dr. Leopold of the Belge Company. He has been in touch with us before. You remember he sold us five grams two years ago. He'll let us have a commission, I'm sure."

"Curse it," exploded Mallory, unappeased: "Some carelessness of yours has caused this."

Keating shook his head despairingly. "I'm sure we'll find it in there somewhere," he said: "Who would steal radium? It could not be marketed. It would be useless to anyone."

But Mallory only grew angrier and angrier. The ruthlessness of the big man was evident in his face, the ruthlessness which had brought him from the ranks of life to the top.

Byfield Mallory was a mineralogist by training, but a roving disposition in his youth had kept him moving. He had prospected for some time, in the Bad Lands of the West. With a man named James Tholl, who had perished in the desert, he had discovered carnotite ores of high radium content, and he had fought tooth and nail against anyone who had tried to interfere with him. He had left all behind; and now, some twenty years later, he was owner of his own company and his own ore deposits.

The big man paid no attention to Moran and Lawson, after the contemptuous short nod to the detective. He stormed at Keating; and at last his anger grew out of bounds, and he shook his fist in the frightened manager's face.

Then Lawson, watching the rage of the man, heard a soft voice at his elbow.

"Father!"

It was the girl who had been in the car. She gave Lawson a fleeting glance. And then, veiling her dark eyes with those long lashes, she stepped past the chemist and Moran and placed her hand on her father's arm.

"Yes, Edith. Just a minute."

"Don't lose your temper, father. Mr. Keating is not to blame, I'm sure. If the radium's in the ruins, he'll get it out."

"He's a fool," growled Mallory.

But his daughter pulled at his sleeve, until the big fellow! turned and accompanied her to the limousine. The motor was started, and they were driven away. Lawson, looking after her, saw Edith's face framed in the rear window for a moment, before she turned back to the task of placating her father.

CHAPTER III
The Mysterious Fog

"WHEW!"

Keating turned to Moran: "What a hell of a temper the boss has!"

"You said it," replied the detective: "Why don't you slam him one on the kisser?"

Keating smiled, as though he might have enjoyed doing so; but then, he froze suddenly, and the worried look reappeared on his face. A workman was coming towards him.

"Well?" asked Keating eagerly.

"Got it turned over, Mr. Keating."

The manager shot away in a flash. Moran and Lawson followed to the edge of the ruins, and climbed over the foundations. The smell of chemicals was very strong.

Keating, in the midst of a group of workmen, was rummaging in the debris. Lawson and Moran picked their way towards him.

They were in the hole which had once been the basement of the factory. The workmen had unearthed the safe which had been used as a storage space for the radium-worth a fabulous sum and yet of such small amount that a man could hold it in the palm of his hand. But one would not hold it in the hand, by any means, if he valued his skin.

"It'll be in a round lead box," Keating was crying to the men: "Look, damn you, look! It may be anywhere around here. It's not in the safe."

The doors of the safe had been blown off and, though there were many papers and various things of value within the twisted steel box, still Keating did not find what he was after. The radium was gone.

"Somebody blew hell out of it, before they let the factory have it," said Moran, looking at the safe with an expert eye.

"If it was burglars," said Lawson, "they'll be damn sorry if they carry that radium around! It'll burn them to bits. Unless expert chemists did it."

"They couldn't sell it, I tell you," cried Keating frantically: "It would be worthless to anyone l" Lawson was silenced.

"What about this phoney fog?" asked Moran: "There was no fog that night, but the watchmen say fog kept them from seeing who came in and blew up the works. They heard a dull explosion inside, they say, and started to the factory to investigate it. They were on the outskirts of the ground, patrolling. Luckily, for them, before they got too near, the whole business went up. The burglars must have planted their T.N.T. and then blown the safe. When they got the radium, if that was what they were after, they slipped out under cover of the so-called mist, and set off the big charge by battery, blowing everything to hell."

But Keating was too perturbed to take in much of the detective's explanation.

"I've got to go and tell him I can't find the stuff. It must have been stolen—but I can hardly believe common burglars would take radium, unless through ignorance, of course. He'll be angry. But I'll have to go and tell him I can't find it."

"We'll go with you," said Lawson suddenly. Moran nodded. The two followed the manager to his car, and were soon driving out into Long Island, where the mansion of Mallory, the Radium King, stood on his great estate.

The Radium King

THE Mallory place consisted of some thirty acres of landscaped grounds. The mansion was of stone, low and massive, surrounded by large trees and fence hedge. Winding gravel drives and paths, running off in every direction from the house, were well kept. The main entrance was through an iron gate where stood the lodge of the gate-keeper, and led under an archway of huge elms. The grounds touched the Sound at their northern extremity.

Moran was somewhat struck by the richness of all this. Keating had seen it before and it had become commonplace to him. What he worried about was, not so much the house, but the man inside it. "He'll be very angry," he kept saying nervously; until Moran growled something about "Telling him to go to hell!"

"Is Mrs. Mallory alive?" asked Lawson, as the manager of the Malloradium Company swung his car around the vast circle before the porte cochère.

"No. The boss is a widower. His wife died eight years ago. Miss Edith keeps house and has charge of the servants. And she knows her business, too. The household is well run. Nobody else except the servants—there's ten of them—lives here. None of Mallory's relations can stand him, he's got too hard a temper. But the girl knows how to manage him. He's not so bad in a way—though he could be a lot better."

Keating drew his car up before the steps. He rang a bell, and a butler opened the door. Lawson and Moran followed the manager; the detective with his matter-of-fact air, though the usual look of abstraction of the chemist was strangely absent as Lawson took his seat in the great reception room.

Lawson seemed to be watching for something, or someone. Moran found it necessary to nudge him; for the chemist did not move, even after the butler returned to lead the way to the second floor.

Keating stepped inside the study—for they were being received in Mallory's apartments.

The Radium King was seated in a dark-blue armchair, his heavy head bowed on his chest, waiting like a lion in his den for his victim. He glared at the three, singling out Keating.

"Well?" growled the big fellow.

Moran twiddled his thumbs, watching keenly but failing to catch Mallory's eye. Lawson, whose abstraction had returned to him, waited.

"I must admit, Mr. Mallory, that the radium bromide seems to have been stolen. There is little doubt left in my mind, though I hate to admit it, that burglars entered the factory, cracked the safe and stole the lead box containing the radium salts.; then blew up the factory to cover their tracks. I have searched over every foot of the debris, but the container is not there. It might have melted down in the heat, of course; but some trace of it would have been found. Anyway, it is obvious that the safe was blown open."

"And what do you expect to do now, my fine manager?" gritted the radium king.

Lawson, who had a sense of humor, could scarcely restrain a smile as he saw Keating's wince of terror.

"Why, there's only one thing to do: allow Detective Moran, and the private agencies, to search for the radium."

"And do you suppose such numbskulls can find such a thing and would know it if they did?" Moran fiushed to the roots of his short-cropped hair. Lawson smiled with his eyes.

"We must be patient," said Keating, swallowing.

Mallory rose and towered over the three. "Curse it," he cried, "curse it! Two years, Keating, two years of work and investment! Fifteen thousand tons of ore, fifteen thousand tons of expensive chemicals, a hundred thousand tons of distilled water, to obtain that pinch of salt! I've mortgaged everything I've got, to beat out the Belge Company.

A Secret Process

"THE new Mallory process, my secret process which made it possible to compete with the foreign monopoly: where's it all now? Damn you! And am I to sit here and twiddle my thumbs, while a few fools look for radium burglars? How about my hundred-thousand dollar guarantee and only four days to deliver ten grams of bromide, purified, to the new Boston hospital? What are you going to do?"

The Radium King stormed up and down the room, cursing, shaking his great fists, his face red with rage.

"I've fought them all," he bellowed: "I've beaten them all; And now—this!"

A light knock sounded on the door. Lawson, nearest it, froze suddenly in an attitude of listening, to shut out the mighty curses of Mallory and hear who might be outside.

"Father!" It was the gentle but firm voice of Edith Mallory. She turned the knob, and stood there, clad in white, Lawson, looking at her expectantly, was delighted to receive a look of recognition. But then she passed him, and went to her father.

"You mustn't go off into these terrible rages," she admonished: "Sit down in your chair and talk quietly."

He obeyed, grumbling. "Fools," he muttered.

Moran stepped forward, clearing his throat. He was taking charge of the situation.

"Well, Mr. Mallory. I'd like to ask you a few questions. Sometimes we're not as stupid as we seem. If I can get some idea of the situation from you—you may be able to give me a lead to work on. First, have you any enemies?"

Mallory glared at the big detective. "Thousands," he growled at last.

Moran was nonplussed. He scratched his head. The girl's laugh tinkled and Moran flushed.

"Do you think such a man as I can go through life and make no enemies?" went on Mallory: "Do you think a man attains my present position without leaving strewn behind him those who have opposed him? Do you think wealth comes to a man because he's kind and polite and lets the other fellow trample on him?"

"No!"

It was Lawson who answered. He stepped into the breach, left by the perplexed Moran.

"Mr. Mallory," he said gravely, "what you say is quite true, but it does not assist us in our investigation. If you want Detective Moran and his organization behind you in your search, you must help us. Can you think of anyone who might have done this to revenge himself upon you? In this question, Moran is quite right. He must have some lines along which to work. As Mr. Keating says, it is highly improbable that any common burglar would steal radium. For where would he sell it?"

Lawson's air of command, and the girl's appeasing presence, calmed the Radium King.

"I had forty chemists and fifty workmen in the plant," said Mallory slowly: "Keating can tell you their names. All the American competitors are out of the field. They were forced out three years ago, as I was, when the Belge Company entered the market. The Belge Company has a practical monopoly at present, because of some high-grade pitchblende uncovered in Africa. It was only through the discovery of the new Mallory process -which is secret—that I was enabled, two years ago, to begin production once again. This process cuts out what were processes number 765 to 853, and 878 to 901. As these were extremely expensive parts of the extraction, I have been able to put radium on the market at the same price as the Belge Company, seventy thousand dollars a gram."

"Then the Belge Company would profit if by chance your supply of radium was lost?"

"Yes! Undoubtedly! But while such an act is possible, it is not probable. Dr. Felix Leopold, who represents the Belge Company in this country, does not like me personally—and I don't like him—but I don't believe he would stoop to such a thing. He is an agent, pure and simple; the Belge Company is well known throughout the world, and is an honorable concern. Besides, if they wanted to fight me, they could undersell me. In all my years of manufacture, even when I was racing tooth and nail with six other companies for supremacy, no such act has ever been perpetrated."

"Then you believe it may be an act of private revenge?"

Mallory shrugged: "How can I say? My mind has been shocked by the disaster. I can think of many who might wish me bad luck, but not one who would do such a thing. As you may have gathered, I have contracted to furnish the new Boston Hospital with ten grams of radium bromide. It is to be delivered Wednesday. I have a hundred-thousand dollar guarantee posted that it will be ready." The Radium King had little more to say. Keating, the manager, had the names of the employes of the company and these were people whom Moran might investigate.

"Shall I get ten grams of radium chloride from Leopold, then?" asked Keating, as they took their eave.

"Yes," said Mallory w'earily, closing his eyes: "Yes. You can get it in shape by Wednesday. The X-Lab will let you have a table and facilities. The other orders are farther in the future, and can wait. Perhaps the stuff will turn up. Offer $25,000 reward for the return of the radium intact."

The three left the big man then, and entered Keating's car.

CHAPTER IV
Dr. Leopold Enters the Case

"WHAT was this secret process Mr. Mallory spoke of?" asked Lawson.

"Oh," said Keating, "I meant to tell you about that! When you mentioned the fact that someone might have blown the factory up for a grudge, and we were talking it over with the boss, there came to my mind the facts of the new Mallory process. Well, one of our young research chemists, a man named Charles Sommers, invented it. He stumbled on it while working with radium salts. Mallory kept him at research work, as he did several of us, including myself. Sommers is brilliant, a great Worker. He has been under contract with Mallory for five years now.

"Here's the point: Sommers' contract called for only fifty dollars a week, as he was just out of the University and might not be of any account. He discovered this process and had to turn it over to Mallory. It became of vast importance to us. Mallory took the process, gave it his own name, and started manufacturing again. Sommers was still working for us at fifty a week. Mallory did not raise his salary or give him any reward. Sommers, naturally, must have been angry and hurt. But he has worked along with us just the same. He did not stand out in my mind as a possible—but no, you'd not think Sommers would do such a thing. He's a scientist, pure and simple, and would never become a murderer and thief. No!"

"Well—let me have his address," said Moran: "Here, when we get to where we're going, you can give me a list of your employes and I'll investigate them."

"By the way," said Lawson, "where are we going now?"

Keating was crossing the Fifty-ninth Street Bridge. "I'm going to see Leopold, of the Belge Company," he said.

"That's another bird we want to see," said Moran. "Ain't he the representative of the company that has had a monopoly on the stuff?"

"Yes. His offices are on Forty-sixth Street."

Dr. Leopold was a nervous little man, with a scraggy moustache. He spoke with a slight French accent. He smiled cordially at Keating, and acknowledged the introductions to Moran and Lawson. He held the latter's hand for a moment, and looked at him keenly.

"Not the Dr. Lawson who published such a competent treatise on 'Gold Colloids and their Behavior in Magnetic Fields'?"

Lawson nodded. Moran's eyes opened. He knew that Lawson had a name in the chemical world; but it was not often that anyone knew enough about chemistry to appreciate his work.

Keating was surprised, too. "I never connected you with that, Dr. Lawson," he said: "I suppose my mind's been off key since the calamity at the works. You heard of that, of course, Dr. Leopold?"

Leopold nodded gravely. "Come inside."

There were two or three stenographers and an office boy in the ante-room, and the doctor led the way into his own sanctum, a room filled with charts, technical books and a chemical bench in one corner, covered with apparatus and small vials of chemicals.

"I still play with chemistry," said Leopold, smiling as his visitors viewed the bench, "though I am little more now than a high-powered salesman. You know, Dr. Lawson, it is necessary to educate our limited clientele as to the uses of radium."

The four were seated. Moran took out a cigar, bit off the end, and settled himself to listen to long names which to him were so much Greek.

"Dr. Leopold," said Keating, "you have heard of the blowing up of our plant. It was done with trinitrotoluol, we believe. Two watchmen were killed. We hoped to locate our radium bromide in the safe; but when we dug it out of the ruins, we found that the safe had been blown open and the radium bromide extracted. The new Boston hospital has ordered ten grams from us. Our plant is demolished, our radium gone; we must fill our order in Boston, however, or lose one hundred thousand dollars. Now, the market for radium bromide is seventy dollars a milligram, is it not?"

Sommers Says "No!"

LEOPOLD nodded gravely: "Yes. But, if you take ten grams from us, we will let you have it at sixty-five dollars per milligram. That will be a brokerage profit of fifty thousand dollars on the ten grams."

"That is quite fair. Mr. Mallory has authorized me to deal with you."

Dr. Leopold rose. "Tell Mr. Mallory how sorry we were to hear of the disaster, will you not?" he said: "One of our executives, Mr. Stephen Tollerman, is here on a visit. He is in the next room, and I will be glad to call him. He would be pleased to meet you, Mr. Keating, and you also, Dr. Lawson. Perhaps he can help us arrange the details of the order."

Tollerman was introduced. He was a tall man, with grey-streaked hair, blue eyes and brown cheeks.

"Mr. Tollerman was one of the discoverers of the pitchblende ores in Africa," said Leopold.

"Well—how soon do you think I can have the radium?" asked Keating, after the amenities of the introductions had passed: "Is it chloride you have?"

"Yes. You know, it is easier to extract the metal in the form of chloride from pitchblende; while the bromide is naturally obtained from carnotite. At present I have no supply on hand; but I can get you as much as twenty grams within eight days. I must send to our bank in Belgium for it."

"Eight days!" cried Keating: "Why, Dr. Leopold, by Wednesday next, we must deliver ten grams to the new Boston Hospital or we lose a hundred thousand dollars! That's our guarantee which is posted to insure delivery of the radium."

Leopold looked at his colleague, Tollerman. The latter shook his head. "The metal can be rushed here by the first boat," he said: "Unfortunately, there are no airplanes to carry it. It will be Saturday next before we can get it. It is unfortunate."

"Mr. Tollerman is right," said Leopold: "Had I anticipated anything of this sort, I would have sent at once for metal, on hearing of the explosion in your plant but we were certain you would locate your radium bromide in the safe."

"But you offered us, on brokerage terms, ten grams of radium chloride not a month ago," wailed Keating: "Where is that?"

Tollerman and Leopold exchanged glances again. Then Leopold spoke.

"It has been rented, Mr. Keating. A research chemist came in and offered us five thousand dollars for the use of our ten grams of salt for two weeks. He said he was in the midst of an experiment. I rented the radium to him, and he has it now."

"What was his name? Where is he?" cried Keating.

"His name is Charles Sommers. He said he had worked for you. He came in only yesterday, and I delivered the metal to him this morning. I asked him about the explosion. He said he hoped you would find your radium bromide in the safe."

"Sommers!"

"Don't you think the Boston people would give you a few days leeway?" asked Tollerman: "We'd like to make the sale to you very much."

Keating shook his head dismally: "The man in charge up there doesn't like Mr. Mallory. He'd be only too glad to make us pay the forfeit. But I can scarcely believe Sommers could have—what did he look like?"

" "He's a personable young man," said Leopold: Of medium height, with fair hair and blue eyes."

"That's Sommers," cried Keating. "The dog!"

Telephone calls—one by Leopold to Charles Sommers, the discoverer of the secret Mallory process, and one by Keating to Mallory, who exploded over the wire—found Keating with permission to deal with the young chemist, and Sommers in Leopold's office, looking cool and collected.

"Sommers," said Keating sternly, "you have ten grams of radium chloride leased from Dr. Leopold. I ask you, for the good of the firm, to turn it back and allow us to fill our order at the new Boston Hospital, where a bank is to be established. This you knew as well as I. What a coincidence that you should come here and rent the only purchasable radium at hand l"

Keating's sarcasm did not touch Sommers. He coolly returned the manager's gaze. "I'm working on something now, in my own laboratory," he said: "To give up the radium now would throw all my experiments off."

Keating grew angry. He stormed at the chemist who had formerly taken his orders. But Sommers was obdurate, he would not give up the radium.

"We stand to lose a hundred thousand dollars," cried Keating, again and again.

At last, Sommers said: "I'll tell you what I'll do, Keating. Give me fifty thousand dollars for my trouble, and I'll deliver the radium back here, and you can buy it!"

Keating, after some argument, called Mallory again. His ear burned as he heard the Radium King's opinion of the matter, but Mallory finally gave his consent.

"We'll just break even on it," wailed Keating. "We save our guarantee, but we lose our percentage for the sale. Sommers gets that."

So the matter was arranged. Sommers promised to return the radium by Monday, and Keating, as a parting shot, angry and frustrated, formally discharged the chemist.

"But my contract," grinned Sommers: "You'll have to pay me fifty a week for the next year anyway."

"All right," shouted Keating: "We'll see! You've held us up, Sommers, but you can't get away with it l"

"Don't forget to bring a certified check Monday," said Sommers mockingly: "And give the boss my love."

CHAPTER V
Clues to Spare

DETECTIVE Moran and Young Lawson, the chemist, sat together in the quiet restaurant, having a belated supper. They talked of the radium theft, and of the many leads which Moran saw with his detective's eye.

"This Sommers now," said the detective, over his steak, "he seems sore as hell at Mallory."

"And no wonder," said Lawson: "But you must watch him, Moran."

"I've got all these fellows listed, who worked there. Some one of them ought to lead us to the thief or thieves."

"The radium should turn up," said Lawson: "Moran, at first, I saw nothing in this case; but I am willing to stay with you now."

"I thought you might be interested," said Moran.

The detective did not guess Lawson's eagerness in the case. He, busy with his work, had failed to catch the young chemist's look at Edith Mallory. But Lawson, whose heart sang strangely for him, had a vision of the young woman before him.

And now, picking at his food, he contemplated ways and means of seeing her again. As Moran's side partner, he might have access to the Mallory home.

The case had not yet shaped itself in his mind. There were too many clues to follow, all vague.

"Radium must turn up, Moran," he repeated, time and again: "No one could have any use for it that I can think of. Save perhaps a research chemist, who could not afford to get it. But that's a wild hypothesis! Take Sommers, for instance. Have you set men on him?"

"Yes, And I've sent shadows to keep tabs on the movements of the whole damn personnel of the factory!"

"The radium should turn up," said Lawson again: "It is only a small inch of white powder, Moran; but if you were to hold it in your hand for any length of time, it would cause your internal organs to alter, and would burn you with ulcers, fatally in the end. Your blood would become anemic, for it attacks the corpuscles and burns good flesh as well as foul. In the hands of a skilled worker, the rays are of immense value in treating malignant growth, cancer, tumors and goiters. Small tubes of glass, with a tiny amount of radium salt, are placed in a wound or on it; the dead tissues are destroyed. But the worker must be protected. Lead-impregnated rubber gloves, a lead screen of some centimeters in thickness, must be used. The gamma rays, which are powerful X-rays in effect, will plow through centimeters of lead. Yes, it is dangerous stuff for a common thief to carry around with him. The stolen radium was in a round lead box, five centimeters thick. In the block of lead were small holes, into which the glass tubes, each containing a gram of the salt, were placed. The cover fitted tightly over the bottom, and the whole was placed in a leather case. The radium could not escape."

Moran shook his head. "It's wonderful stuff," he said: "Somehow, I hope, when I find it, it's still safe in that lead box!"

"Moran," said Lawson, leaning across the table, "a skilled chemist took that radium! I'll bet you a nickel I'm right. It would take such a man to handle it. And someone with a grudge, too, or he would not have destroyed the plant!"

"Enemies? Sure!" Moran grinned: "Thousands! Far as I can make out, everybody dislikes old Mallory. He's a son-of-a-gun! Don't like him myself."

"It might have been Sommers, of course," said Lawson: "And then again, it might have been any of the others who worked for him. But watch Sommers carefully."

"And what about Leopold?"

Lawson was silent: "I don't know. As the thief, he seems actually impossible to me. I don't think the Belge Company would go to such extremes to ruin Mallory. Besides, if they knew the radium was gone, they would have had some at hand to fill the order."

"Maybe they're in league with Sommers."

"Possible. But not probable, because why should a man like Leopold bother to shake Mallory down that way? He could easily have raised the price a little, if he wanted some for himself. That's all. But better keep your eye on Leopold as well."

"It's some job," said Moran, shaking his head. "There's too many clues; but none of them, except perhaps Sommers, points anywhere. However, I fill get to work right away."

"How about the fog?" asked Lawson.

Moran threw down his napkin with a curse: "I'm going crazy, trying to get a start on this business!"

The Marauder

YOUNG Lawson, research chemist of the Margeaer Society, stood with one test tube held over another. It was the middle of a busy day. Outside, in the general laboratory, the rank and file of the chemists worked on milk cultures and general analysis. Lawson, in his own room, a privileged being with a free hand to experiment as he would, was strangely disturbed.

And, for the first time, it was not the atoms and electrons which held his interest; no, he was upset that he could not concentrate on them as he should.

The radium case, on which he had promised to help Moran, had baffled him; for there was no way to get a start at working.

However, Lawson, whose single passion had been chemistry, found the science less absorbing than formerly. Between the retorts and reactions had interposed the face of a woman. Lawson, supposedly hard at work, was idling his time away in dreams of Edith Mallory.

He had seen her but twice. For three days now—it seemed three eternities to him-he had not had a glimpse of her.

Detective Moran had been out working, directing the search for the radium thieves. Lawson had had no word from him; for, when last they had met, Moran had said he would call on Lawson when he got a workable clue. And no word had come.

The chemist poured slowly from one tube to another. Red turned to green, then to deep blue. He cursed and threw both tubes in his waste barrel. A graduated tube, in which was a pink liquid, with a rubber hose clipped shut at the bottom, occupied him for a few moments, but he was restless. His hand trembled, and too much liquid entered the beaker.

"No use," he muttered. He stood for a time in revery; then he evidently came to some decision.

Taking his hat and top coat, he left the laboratories, and went out into the sunshine. He sighed deeply, and started towards the river. For the rest of the afternoon, he alternately walked and sat on benches, thinking of the girl.

Towards seven o'clock, he remembered he had not eaten all day; so he dropped into a restaurant and drank coffee. A phone booth in the place invited him to call Moran—for Moran might have some news of Her. But Moran was not in; had been out all day, according to the sergeant who answered.

Darkness had fallen when Lawson, the man of science, finally walked with faltering steps to the Pennsylvania station. A Long Island train took him to the town on the outskirts of which was Mallory's estate.

He hoped to have a glimpse of the girl. Perhaps, his heart said, she would appear at a window, might even come out, and, seeing him, speak to him. He sighed. His brain called him a fool; but he could not resist his desire at least to see the house in which the idol of his dreams lived.

It was some time before he could muster up his courage to go by the grounds of the estate. There was a light in the lodge, at the big gate, and the chemist shunned this place. But there were smaller side gates in several spots, and Lawson, taking his courage in hand, slipped into the grounds.

The big mansion, set back among the trees, was lighted in several of the downstairs rooms. Mallory's apartments, in the rear, were dark.

He crossed the lawn stealthily, ashamed of himself, his heart beating hard. He had no right there, he knew.

Would she appear? A glimpse of her at the window and he would have felt rewarded.

He stood within fifty yards of the mansion, and tried to muster up courage to go and ring the front door bell.

So absorbed was the chemist in his thoughts, that he did not see the stealthy dark figures which crept towards him across the lawn skulking in the shadows of shrubbery, crawling almost on their bellies across the open spaces.

Suddenly, he was leaped upon from behind, and with a stifled cry, he felt himself borne to the grass and held in a grip of iron.

The Gunman

"KEEP still, you," growled a heavy voice, and the muzzle of a gun was jammed into his ribs.

They searched him professionally, but found no weapons. Lawson, chagrined, at the mercy of the men who had leaped on him, found all his natural fear of the attack submerged in the ignominy of his position.

More figures were running across the lawn. Lawson, with infinite relief, heard a familiar voice.

"What have you got?"

It was Detective Moran. The sturdy figure stood over the prostrate Lawson, as flashlights illuminated the chemist's face and form.

"Well, for the love of heaven!"

Moran stared at his friend for several seconds. "Get out of here," he snarled at his men, who had brought the chemist down: "Don't you know Dr. Lawson?"

The others retired. Moran pulled Lawson to his feet and brushed off his clothing. "Fools!" he repeated.

Lawson laughed: "I'm the fool, Moran. I did not know you were out here. What's up?"

"We got a call last night that marauders were around the estate," said Moran. "Mallory asked for police protection. I thought we'd caught something when we got you."

"Marauders?"

"Yes. Mallory and his daughter were out. They sometimes go to the city together, to a show. One of the servants, who happened to be in the front of the house to answer the telephone, heard noises outside. He looked out, but could see nothing because of a fog that had come up."

"A fog, Moran?"

"Yes. I thought maybe, being near the water, there'd been one here; but nobody in the neighborhood saw any fog. However, this footman says there was a fog and he couldn't see anyone outside. He went through the house downstairs, but found nothing. He returned to the servants' quarters and got the butler and a couple of other fellows, and the four of them went outside, and they all claim they were in a thick mist. Finally, they went upstairs. They came to Mallory's quarters, and found distinct signs of an intruder having been there. A window was unlocked—a window which gives out onto that low balcony you can see at the rear of the house. But they didn't catch anybody. They reported the incident to Mallory when he returned, and he called me and asked me to send some men out."

"Was it burglars, do you think?"

Moran shook his head slowly: "They didn't steal anything, if it was. Of course, they may have been frightened off."

"And then," said Lawson, "there's the matter of that fog, eh? Strange it should happen twice!"

Moran nodded gloomily: "You said it. It's got me."

"Anything else?"

"No. I haven't got the full reports in yet. I've got men on the whole shebang. But tell me—how is it you're out here?"

The detective looked searchingly at his friend. But the light was dim, and the detective missed the flush which Lawson could not restrain.

"Oh—I came out to have a look around."

"I hoped maybe you had something and were looking for me."

"No." Lawson came to a sudden decision: "Moran," he said, "appoint me a shadow, will you? Let me keep my eye on the mansion. I'll work for you out here."

"Huh? Why should you waste your time fiddling around here?"

"I'd like to, that's all."

"Well—if it'll give you any pleasure, stick around. I'll not be out much. Was just getting the boys set. We'll watch for a few days and then, if we don't catch anybody, we'll figure it as burglars."

"Did you find any footprints?" asked Lawson.

"Oh, a couple, in the grass below the balcony. But whoever it was traveled on the gravel paths. He left no trail."

CHAPTER VI
The Lead Box

"SUBJECT came out at 8:45 A.M. Walked to bakery, where he purchased ten cents' worth of rolls. Returned home. Greeted by wife, blonde, about twenty-six. Remained indoors all day, in the rear of house, where he has a chemical laboratory. At six P.M., appeared with wife; and the two went to supper, both in high spirits. Then to theater, a musical comedy. Went home and retired. Met no one. Nothing unusual from regular routine."

"Can you beat that?" said Detective Moran, despairingly, handing the sheet to his friend Lawson.

Lawson looked over the operator's report. Four of Moran's best shadows, man-hunters who missed nothing that went on, had been set on Charles Sommers, the young research chemist who had shaken down the Malloradium Company for fifty thousand dollars. For ten days, he had lived quietly at home; experimenting in a small laboratory of his own in the attic of his suburban home; going out occasionally, but acting in no way suspiciously. Likewise, the other employes who had worked for Mallory had been shadowed. It had taken a hundred men to investigate them; and of all these possibilities not one had proved of value.

Nothing had come of the watch outside Mallory's home. Lawson had spent most of his waking time on the grounds. He had been rewarded several times by a sight of the young woman, Edith Mallory. Once she had seen him, during the day, and had smiled on him.

But, now, he no longer had any excuse to visit there, for Moran had called off his shadows in disgust. The marauder had failed to walk into the trap set by the police.

"And Leopold?" asked Lawson, who was seated on Moran's desk, swinging his legs as he watched the lines of worry on his friend's brow.

"Hell," exclaimed Moran: "Nothing there, either. Leopold has not stirred from his regular life. Sommers went and got his check Monday from Keating. He met Leopold and Tollerman and Keating. I was hidden, to observe them. Sommers laughed in Keating's face. Now, plenty of employes of Mallory have been moving around. One chemist, named Smythe, went all the way to Buffalo, and I thought we would get going; but he was only after a new job. It was the way with all of them; they were after a new place to work. That was natural enough, since they were thrown out by the wrecking of Mallory's plant."

The radium bought from the Belge Company and obtained from Sommers, had been delivered on time to the new Boston bank, at the hospital; so that Mallory had saved the forfeit money.

"What's Keating been doing lately?" asked Lawson.

Moran grinned: "Still looking for that radium in the ruins. Guess he's been over them fifty times! He'll never find it."

Just then the phone rang at Moran's elbow. The detective picked up the receiver. He listened for some time.

"Well, for the love of heaven!" He hung up and turned to Lawson. "They've found the radium! Keating just called me to tell me he discovered the box within a few yards of where the blown safe was."

Two hours after the news from Keating of the finding of the radium, Moran, accompanied by Lawson, stepped from their car to the front door of the Mallory home. They were taken upstairs to Mallory's apartments.

The Radium King was strangely subdued. He was almost polite to his visitors; if a quiet voice and a disposition to listen without interrupting can be termed politeness.

Keating, radiant and happy, was there. In his hand he carried a round leather case. Inside the case was a heavy lead box, with walls some two inches in thickness, and inside the box were holes into which fitted small glass tubes containing amounts of white salt.

"Boss, it was wonderful," he cried: "I swear I looked there a hundred times before! But today, I was poking around as usual, and I happened to turn over a burned board; and there, lying right in front of me, was the case!"

"I'm very glad," said Mallory: "I've not been well lately, Keating. The loss of that radium would have just about ruined me. Now we can fill our other orders. Do you think there's any chance of the Belge Company buying the extra ten grams from us?"

"I'll see. They might help us out."

"Let's hope so." Mallory turned to Moran: "I'm very much obliged to you for your assistance. I'm sure you've done everything possible to help us. As there were no thieves to catch, it's no wonder you didn't do it."

"I'm happy to have been of assistance," said Moran, "and glad you've recovered the radium. We'll call our men off now. Any time we can help you out again, let us know."

Lawson, standing quietly behind his friend, had a sinking of the heart. While he tried to rejoice that the radium had been found, still he knew that he would no longer have any excuse to see Edith Mallory.

The girl came into the room, as the three were about to leave. Mallory, who had, on the previous occasion when they met there, been too wrought up to remember small things like the social amenities, introduced his daughter Edith to Moran and Lawson.

CHAPTER VII
A Fresh Stimulus

THE chemist took the small hand she graciously held out to him, and a thrill passed through him.

"I'm happy to know you," she said.

Words, which could express so little! Lawson mumbled incoherently. He found courage to look into her eyes. He caught the kind gleam of them, and the recognition of himself.

"Come along, Lawson," called Moran, from the doorway.

Keating was jubilant. "Everything's O.K. now," said the manager: "The boss will have to admit I was right, and so will you, gentlemen. I knew no one would steal radium."

"Well," said Moran, "it sure looked like it for a while. It's still a puzzle to me."

"What are you going to do now?" asked Lawson. "I'm going to put this radium bromide in a safe place," said Keating: "In the thickest, best-guarded vault I can find. Then I'm going to go and see Leopold and find out if he'll refund us our money on the stuff we bought from him. I think he will. The Belge Company has always been every decent in its dealings, and will hardly refuse my request. I hope the boss gives me that $25,000 reward."

Lawson was sad. He had met Edith Mallory, only to lose his opportunity of seeing her again. He had no excuse now to go to the mansion, and there was little chance that he would ever meet her in the natural course of events.

Then the chemist, about to enter Moran's car, had an idea. Keating! He would become friendly with the manager, and in that way, he might be able to establish contact with Edith Mallory.

"I'll see you again soon, Moran," he said, hurriedly.

The surprised detective watched Lawson as the latter spoke a few words to Keating and then climbed in the manager's car.

"He's been acting funny lately," thought Moran. But cases had been piling up and the detective knew there was plenty of work awaiting him at headquarters. He started off, waving goodbye to the two behind him.

Keating, talking rapidly, well pleased with himself, drove into the city, and stopped at a bank vault, where he deposited the lead box. Lawson, tagging after him, accompanied him next to the offices of the Belge Company.

Leopold was there, and when Keating and Lawson were shown in, he received them cordially.

"We've found our radium," said the manager.

"That's good news. I thought you would." Leopold was glad: "It's an unlikely thing for anyone to steal. But how can I help you now?"

"I've come to see about getting a refund, selling you ten grams of our stuff," said Keating.

"H'm. It's disappointing to lose a sale; but I think it would only be ethical for us to consider it. I will have to cable abroad and confer with Tollerman about it. I think it can be arranged. That is, we will take ten grams off your hands. Naturally, you lose your commission."

"That's fair enough. Let me know what the result is as soon as possible."

"Yes, surely."

Keating was a busy man. Lawson was forced to leave him soon after, for the manager was oblivious to the chemist's desire to become better acquainted.

Lawson returned sadly to his rooms.

He was again called from his laboratory, two days after his introduction to, and what he feared would be his last sight of, Edith Mallory.

"Hello, Lawson, 's Moran."

"Yes? What's the trouble?"

"Plenty! Keating was just here."

"Well?"

"Can you come over? I'm at the office."

"Yes. I'll be right there."

In Moran's office, the detective grinned at his friend the chemist:

"We were right, after all. That radium was stolen."

"I thought it was found?"

"So did everybody. Keating did, Mallory did, I did and you did! D' you know what happened? Keating gets the Belge people, Leopold and Tollerman, to say they'll take back ten grams to make up for what Mallory had to buy from 'em. So he delivers the ten grams this afternoon; and he calls me to report that on analysis the salt in the lead case was nothing but salt!"

"You mean common salt?"

"Yeh!"

"Sodium chloride!" Lawson passed his hand over his brow: "Heavens, Moran; what do you make of that?"

"Don't know. Can you figure it? It wasn't possible for the Belge Company to crook Keating, because he himself was right there while they looked over the stuff!"

A Cruel Trick

LAWSON, with knitted brow, rose and paced up and down the room. "This will be a blow to him-and to her," he murmured.

"Eh?" said Moran.

"Nothing."

For several minutes, the chemist ruminated: "Weren't there men watching the ruins?" he asked.

"Yes. A couple of guards."

"And did they have anything to say?"

"Keating never questioned them after he found the radium—or thought he had found the radium. But today, I went and located them. D' you know what they said?"

"Yes," said Lawson suddenly: "They said that the night before Keating discovered the radium, there was a thick fog over the ruins. And there was no fog, anywhere else."

"You're right."

Lawson ruminated for some minutes. Then he turned on Moran. "Moran," he said, in a grave voice, "there is an evil spirit operating in this case. What a cruel trick that was, to plant the radium case with common salt! It is consistent, however, with the operations of this unknown person, who all along has played his hand well. Moran, I'm going to find him."

"That's the way to talk," applauded the detective: "I'm putting men back again on Sommers and the rest. "Only—well, if Sommers had planted that stuff, we'd have trailed him to the works and caught him red-handed! See? This only throws us out of gear all the more."

"I will find him," said Lawson. Then he added, under his breath, "for her!"

* * * * * *

It was late afternoon. The red sun was sinking behind the trees of the Mallory estate as Young Lawson, in a hired cab, drove up to the great gate and was admitted by the lodge keeper. A few moments later, and he was inside the reception room, waiting with strangely beating heart.

A light step sounded from the corridor, and then Edith Mallory stood before him.

"Hello, Dr. Lawson."

She held out her hand and smiled on him. He could not speak for a moment as he looked at her. It was her air of quiet assurance that had charmed the chemist as much as her beauty; that, and an attraction towards her which amounted to magnetism.

She sat down, and he took a chair near her. She waited, after a conventional remark or two on the weather. Lawson at once came to the object of his visit.

"Miss Mallory," he said, trying to be as businesslike as possible, "I don't know whether you know just who I am or not."

"Mr. Keating told me something about your work and reputation," she said. Then she added, smiling, "I asked him about you."

Lawson flushed with pleasure; but he strove to stick to facts. "I have come to help your father and you in this business of the stolen radium," he said: "I want to get all the facts possible from your father. Now that the thief or thieves, whoever they were, have appeared again, it is obvious that some malignant entity is working against your father. Anyway, I am sure we have to do with a man who knows chemistry, and knows your father and hates him. The first, I believe because of the way the radium has disappeared, and the planting of common salt in the lead box. What use, beyond the fact that the loss of the radium bromide might ruin your father financially, the thief intends to put the radium to, I cannot even guess. It can't be sold, that's certain. It's value is too fabulous for the thief to realize even a fraction of its worth. He is evidently an enemy of your father, for the spite of returning to plant the sodium chloride; raising your father's hope and then dashing it to the ground, and the fact that marauders have been upon the estate, point to this."

The girl listened gravely.

"I fear the same thing," she said: "Some person wishes to ruin father. But why did the marauders come here? The theft of the radium is enough to cause bankruptcy, the expense of its extraction is so great. What I fear now, is that this enemy may have come to kill father!"

Her fists were clenched. She was nervous, under her forced calm. Lawson—who had thought of the same thing, but had not wished to alarm her to too great an extent by telling her that he believed the marauders had come to kill her father and been disappointed because Mallory was out—could only nod.

"Well," he said, reassuringly, "the thing to do is to set guards about the house again. Do you think I might speak with your father now?"

The girl shook her head: "Father is not well. The worry and anxiety about the radium has, I believe, made him ill. So our physician, Dr. Morse, thinks, too. He has dermatitis and has grown so irritable that I'm the only one who can talk to him."

"The radium should turn up some time," said Lawson. "The burglar could scarcely use it."

She nodded. She rang a bell and ordered tea. The two chatted of this and that, and the young man was pleased to discover that Edith Mallory knew a great deal of chemistry. She had taken a course in the university in science.

Two hours passed so quickly, that Lawson was amazed to realize that it was dark, and his wrist watch said seven o'clock.

"I am going to begin my own investigation," he said: "You see, while I work for a private company, Moran lets me assist him sometimes. I have solved a case or two for him."

But he had already told her the history of his eventful chemical life. She smiled on him as he shook her hand.

"If I can help you, at any time, don't hesitate to call me," he begged: "Here are my office and home phone numbers. I'll be glad to assist you at anytime."

She thanked him, and accompanied him to the door. The chemist walked down the gravel drive which led to the gate, with wings on his feet, and a song in his heart.

CHAPTER VIII
More Guards

THE chemist went to Moran's office, and waited until the detective came in.

"What's up?" asked Moran.

"I was going to ask you the same thing," said Lawson smiling: "Moran, my theory is that the man or men who were out there that night on the Mallory place, came to kill him. I don't believe you ought to leave it unguarded. There is Mallory's own staff around, but you know they can't watch a place the way your shadows can. Send out Harte and Ulman."

The detective was unconvinced: "I figure it was just some second-story man," he said. "I've got Harte and Ulman on young Sommers. You know, we've sent out warning to all the possible places where radium might be sold, to let us know if any which can't be checked turns up."

"That's right. But better send your two best shadows out to Mallory's. I want them there."

Moran scratched his head. "You been out there?"

"Yes. Two hours."

"Did you see Mallory?"

The chemist flushed slightly. "No, Moran. I was talking with Miss Mallory."

It was a long time before the detective spoke. Lawson sat under the light, and Moran, after looking at him for some seconds with a puzzled face, began to smile. The smile started with his eyes, then spread to the cheeks, then to the lips, and finally became a broad grin.

He slapped his leg, and drew back his head. "Now I've got you," he cried delightedly: "By golly, it's funny I didn't guess it before!"

"What?" said Lawson testily.

"Go on! You can't kid your old friend Moran. You're sweet on that girl!"

Lawson was irritated, but he knew that to allow Moran to see it would only please the detective. He waited until Moran's mirth had subsided.

"Whether that's true or not, Moran," he said, "we're got to find the radium."

"All right," said Moran. "You've helped me plenty, and now I'll help you. I'll send Harte and Ulman out there tonight. No one shall touch a hair of her head if I can help it."

So the two shadowers were dispatched to the Mallory estate.

* * * * * *

"Now, listen, Moran," said Lawson: "Somebody is trying to get Mallory. That's almost obvious. They have broken him by stealing this radium, and now I think they want to kill him. They were disappointed when they got out there and found him not home."

"None of these fellows we're watching was out there," said Moran.

"Then it was not one of them. But it might have been an accomplice."

"What do you suppose all the talk about fog was?" asked Moran.

"That is the simplest thing in the whole mystery," said the chemist: "Why, Moran, what do you do when you have a criminal bottled up in a building and want to get him out without exposing yourselves?"

Moran slapped his knee. "Why, of course! You mean it was just a smoke screen?"

"Yes, that's it. That's another reason I say a chemist is at work. But we must not let anything slip, Moran. There are only a few works where such gases are made. Look them up, and see if you have any luck that way. But, personally, I believe the criminal manufactures the stuff himself. It's easy enough. Silicon tetrachloride, for instance, is a colorless liquid, but when it comes into contact with air, it gives off thick white fumes. The water in the air decomposes it, forming silicon hydroxide, a white substance, and hydrochloric acid. Also, if dry ammonia is mixed with the silicon tetrachloride, more white clouds will be formed; because the hydrochloric acid unites with the ammonia to become ammonium chloride. This and titanium tetrachloride were much used in the war to lay smoke screens, Moran; the smoke screen is also used by you fellows to protect yourselves in the open against desperate bandits. What would prevent the bandit turning about and using it to protect himself?"

"Makes no explosion when it starts, either," said Moran: "Well, that's that. I'll look around and see if I can locate anybody who's been buying smoke."

"Probably the thief makes it himself. As I said, I believe we have to do with a man familiar with chemistry."

The Call

SEVERAL days had passed. Moran had reported no luck with his investigations. Harte and Ulman had not been able to catch any trespassers on the estate, but, acting under orders, they alternated with another pair of shadows who watched during the day.

Lawson had been in touch with Keating. He had requested the manager to rack his brains, in the effort to think of someone who might be so bitter an enemy of Mallory as to plot destruction and death for the Radium King.

It was the absence of a visible motive which blocked the investigators at every turn. There were plenty of men, like Charles Sommers, who might wish Mallory bad luck; but no one could be traced who would go to such lengths to get revenge.

Lawson had promised to find the stolen radium; he had told Edith Mallory that he would do so. He had been out to the estate twice again to search for traces; but the ground had been trampled by many feet, and nothing remained, even if there had been anything in the first place. He had spoken with Miss Mallory on both occasions, but her father had been growing worse.

'Lawson sat in his bachelor quarters that night, his feet on his desk, slumped down in an armchair. His head rested on his breast. His thoughts reviewed the radium theft, but always returned to the girl.

It was about eight o'clock. The phone bell rang, and Lawson, picking it up from its stand, answered. His heart leaped when he heard the voice of Edith Mallory.

"Dr. Lawson?"

"Yes. Miss Mallory?"

"Yes. Dr. Lawson—" there were tears in the voice—"I—I am calling to ask your help. Father is worse. The physicians say he may die. I—I don't know what to do. He has growing sores on his body and his heart is in terrible condition. I don't know where to turn for help. You told me to call you if I needed you."

"Yes, of course. Will you allow me to come out there?"

"I wish you would."

"Is your father delirious?"

"Yes, he is at times."

"I will come at once."

The chemist packed a bag, and caught a train. He arrived at nine o'clock, and was admitted by the gate keeper. He was aware that shadows, watched him and knew that Moran's faithful bloodhounds were on the job.

The young woman greeted him with tear-strained face. "Father is in his apartment," she said: "He has been in bed now for several days. He cannot eat, and is growing weaker."

Lawson's heart was torn, by the sight of the girl's grief. He tried to comfort her but she loved her father and her inability to help him made her frantic.

"Something must be done! Something can be done," she cried. "Oh, help me!"

"May I talk with the physicians?"

"Dr. Morse is here. There are two skin specialists, but they come in the morning."

Dr. Morse was a heavy-set man, with clean-shaven face and black eyes. He seemed rather to resent the intrusion of Lawson, whose degree was Ph.D. But he came out into the hall at Miss Mallory's call, and answered Lawson's questions.

The Evil Attack

"YOU say ulcers have appeared, after dermatitis?" asked Lawson.

"Yes. And the internal organs are deranged. The heart and stomach are not functioning properly. Also, a blood test shows pernicious anemia."

"Well, then, Dr. Morse," said the chemist, "this points to exposure to radium. Do you realize that?"

The doctor shrugged: "My dear fellow, we have diagnosed it as such. We are treating the burns with scarlet red and zinc oxide. To keep them clean and prevent their spreading is the most we can do. What baffles us is that the patient shows no improvement, but grows steadily worse. It is easy to see how he might have been burned at some time during the course of his work with radium. The burns may not appear for as long as two years, and, again, they may show in ten days."

Lawson nodded. From the other room, a shriek went up, an eerie cry which penetrated the flesh and caused the girl to scream in terror and sob violently.

"Oh, poor father!"

"Hush," ordered Lawson, gripping her arm. The chemist stepped into the sickroom, lighted by a single lamp. A white-clad nurse hovered near the patient.

Mallory heaved on the great bed.

"Fire," he cried: "Fire! I see fire! Oh, God, my eyes!"

The Radium King, a broken, pitiful creature now, writhed in agony.

"James—Nora—Edith. My eyes! Curse the luck."

The chemist's high brow was corrugated with heavy wrinkles. Outside the door, he could hear the sobs of his sweetheart, crying for her parent's pain. Lawson stepped outside the room.

"Doctor," he said gravely, "do his words mean nothing to you?"

"Eh?" said the surprised Morse. "They are ravings, that's all."

"Perhaps they are. But they have a significance. Now, I want to investigate the room. Please tell the nurse that I am to be allowed the run of the place."

Morse hesitated. He did not like this interference with his authority. "Of course, doctor," said Edith Mallory, "allow Dr. Lawson to do as he likes. He is a friend and a famous scientist."

The doctor stepped aside. Lawson entered the sickroom again, closing the door after him.

Fifteen minutes later, he came out, his eyes grave.

"Dr. Morse, you must move Mr. Mallory at once. Do not allow anyone to enter the room again, or the bed to be used."

"The patient should not be moved," said Morse, "in his present condition."

"He must be moved. I will move him myself if you do not. He is burned by radium, and he is being burned more. I don't want anything disturbed in the room, but Mr. Mallory is to be taken to another bed."

"On whose authority do you issue these orders?" asked Morse coldly.

"On my authority," said the girl, her eyes flashing.

Morse obeyed, grumbling. Ten minutes later, and the sick room was empty. Mallory had been carried down the hall, and placed in a guest room.

Then the three, Morse, Lawson and the girl, went downstairs. The nurse was left in charge of the patient.

"I'm going outside for a minute," said Lawson. He went to the front door, and stepped out into the night. "Ulman, Harte," he called softly.

A moment later, and a dark figure stepped up to him: "It's Detective Ulman. How are you, Dr. Lawson?"

"Very well. But I want you and Harte to watch Mr. Mallory's former room very carefully. It's the fourth window from this side, in the rear, where the balcony is."

"Harte is there now."

"Very well. Don't let it out of your sight for an instant. Keep under cover yourselves, so you will not frighten anyone away, do you understand? If anyone comes, let him get into the house; but do not let him out."

"Yes, sir."

Lawson returned to the hall, where he found Morse about to take his leave. "I'll be here in the morning," said the doctor: "If he grows worse during the night, call me at once."

The girl and Lawson were left alone.

"Why did you have father's room changed?" asked the woman.

Lawson's eyes were grave. "Because, Miss Mallory, from your father's words, uttered in delirium it is true, but significant to me, I became almost certain that he was being exposed to radium. It makes the eyeballs luminous—not so that it can be seen by an observer—but the exposed person's eyes gleam under the lids so that, when the eyes are closed, there is a glow which is maddening. This is but a temporary effect of radium; it would have passed off instead of growing worse, had your father been burned at any previous time. That and the fact that he is only getting worse, made me sure that he must be under the influence of radium while he lay in bed.

The Deadly Enemy

The girl gasped: "Then you think—"

"I think there is a cruel and deadly mind with which we have to deal," he said: "It is for this reason I do not wish anything to be disturbed. Have the reporters been calling you at all Miss Mallory?"

"Yes. Every day, to ask how father is. It is known he's ill. All our acquaintances inquire, too."

"Well, when they next call, tell them that he is much better and will get well. Tell them that he has been removed to another room, but do not give the real reason. This is important. Will you do that?"

"Why, of course. But do you think he will recover?"

"Yes, I think he will get well. Now that he is out of the radium's vicinity, he ought to improve rapidly if correctly treated. But report it as already accomplished, will you not! Tell the doctors to do so, as well. It is important."

She sobbed with relief, as he repeated that he was sure her father would recover. He could not resist taking her hand in his.

"Oh," she cried, "I knew that you would help me! I felt it, Dr. Lawson."

"Call me Young," he begged.

"Yes, of course I will. And you'll call me Edith, won't you? It's been hard, to have no one to call on, no one to depend on. Father and I have always been close together. In spite of his temper, and many bad points, I adore him. He's always been good to me."

"I love him for that, then," said Lawson, in a low voice.

The girl grew calm as the chemist talked to her soothingly.

"Will you stay here?" she asked: "You can have a suite."

"Yes. I thought I might be needed, so I brought a bag. I have been growing steadily suspicious concerning the proximity of radium to your father; and I wish to see if I cannot trap the thief. I will tell you that I have located the radium stolen from your father, of that I am almost certain."

"Oh," she murmured, "I think you're wonderful!"

"I have in my bag a spinthariscope, an instrument used in identifying radium emanation. It is formed of a zinc-sulphide screen, which glows when the alpha particles strike it There is a magnifying glass which helps to identify the glow. You know, it is thus that the luminous paints used on clock dials are made."

She accompanied him to the door of the bedroom which her father had formerly occupied. Lawson ordered her to remain outside.

"It is dangerous to enter the room," he said. "I will not be surprised if the nurses and physicians develop burns."

"But you," she cried. "If it is dangerous for me, it is for you!"

She held him back, and would not allow him to make the test for /radium then. He promised to wait until the next day, when he would be able to go to the city and obtain lead impregnated gloves and a screen behind which to work.

"I do not know just where the radium is hidden," he said, "but I will locate it. However, I wish to leave it there for a few days."

As the chemist said goodnight to the girl, she threw her arms about his neck, and kissed him. He seized her in his embrace.

"I love you," he cried. "I love you!"

"And I love you," she murmured.

CHAPTER IX
The Radium Found

Young Lawson awoke in the great Mallory mansion with a sense of joy. He sprang from bed, and greeted the sun which streamed in at his window with a smile, for it pleased him that nature should be happy. It was in the fitness of things.

He dressed and went downstairs. Edith was before him, and greeted him with a kiss. "Father's better," she said: "He slept well. When I tell everyone that he is recovering, it will be the truth. And, if you have found the radium, it will make him happier, and help him along; for his affairs would have been in a bad way had it been lost. The factory, though insured, was heavily mortgaged—as is this place. Fighting the foreign monopoly has been expensive, as well as the production of the radium bromide. But there are several orders to be filled, in the near future, which will set father on his feet again."

"Well," said Lawson, "I assure you I am certain that the radium is hidden within the room where your father was lying. Near his bed, probably. That explains the marauders who came upon the estate. They came to plant the radium so that your father would be burned. Far from being disappointed, as I first thought, that he was not at home, they waited for an opportunity to get in while you and your father were out. The footman must have heard them when they were leaving, after the work of hiding the radium was finished. By the way, your father mentioned 'Nora' several times in his delirium, as well as yourself. Who was she?"

"My mother," said the girl. "She was so good, and kind, Young. She always tried to make father control his temper. I can remember her soothing him from the time I was a little child. They met in Colorado, while father was prospecting out there, and before he became rich."

"And 'James'-who was he? Your father also mentioned that name?"

"That was James Tholl, my father's friend, who perished in the terrible Bad Lands over twenty years ago."

It was all Lawson could do to tear himself from the girl's company. He had business to attend to, however, and he went into the city and visited two or -three places. He returned in the afternoon, and found that his equipment had been already sent and was awaiting him.

"Several of the papers called, and I told them father was getting better," said Edith.

"Good. Now I must go to work in the bedroom where you father was, and where I am sure I will find the radium."

Lawson, with the aid of the butler John, carried the lead screen and his other equipment to the door of the chamber. There he donned a helmet made of lead rubber and gloves of the same material.

"Here's the spinthariscope³," he said, showing the girl an instrument which looked like a fat microscope: "There is a zinc-sulphide screen in it and, by placing a small amount of radium within and looking through the glass, it is possible to see tiny flashes as the alpha particles strike the screen. But first, I must locate the radium."

3: Spinthariscope. A device for showing fluorescence due to radium by the scintillations caused by impact of the alpha rays thrown off by it against a fluorescent screen.

Lawson, pushing the screen before him, entered the room which had almost become a room of death. The girl, standing in the corridor, listened anxiously.

For some time, Lawson remained within the room. She heard him pulling down the dark shades, and walking about. At last, he came out.

"I have found it," he said.

"Where was it?"

Lawson shook his head sadly: "Darling, someone has tried to kill your father in a horrible and cruel way. A slow death was plotted for him by this unknown assassin. The radium bromide, stolen from your father's factory, is hidden in the folds of the mattress in glass tubes. They are protected from breaking by the layers of wool. A seam was ripped underneath, and then sewed up carefully; so that it could not be seen from a superficial examination such as a maid might give in making up the bed. I took out only one tube, and subjected it to the spinthariscope test; and it was radium. I am certain that the full thirty grams which were stolen are hidden in the mattress. It is no wonder that your father is in such condition."

The full realization of mysterious evil, brought on by this concrete evidence that the radium was really within her father's former room, put there by a malignant hand, caused the girl to cry. Lawson comforted her as best he could.

"Now, darling, don't tell anyone we have found the radium. I wish to trap the thief. You are sure that you told the papers his room had been changed, and that he was much better?"

"Yes."

"Then, if the assassin is as desperate as he has so far proved to be, he may make an attempt to recover the radium. Also, I must ask Moran to send more men out here, to guard your father's life. If the man or men who are trying to kill him have gone to such lengths, they may go farther."

The Trap

TWO more of Moran's men were now stationed outside Mallory's present room, several windows down, on the same floor as the bedroom where the Radium King had been almost burned to death by his own radium.

"Watch closely," ordered Lawson: "Allow anyone who comes to enter the room where Mr. Mallory formerly was. In case you see anybody climb that balcony and try the windows, tap on the library window. I will be in there. Be sure I answer you; this is important. But—more important still—do not allow anyone to get into Mr. Mallory's present chamber."

The shadows promised faithfully to obey Lawson's orders.

The chemist passed the evening happily with his sweetheart. She depended fully on him now.

"You're wonderful," she repeated, over and over.

Though Lawson had come in for more than his share of scientific accolades, the admiration expressed by the girl meant more to him than all the rest.

She went up, every half hour, to see how her father was. Mallory had been able to eat. Dr. Morse reported his heart improving; and the radium burns, while terrible, were no longer spreading. He slept a great deal, and was quiet.

But Lawson, occupied though he was by his conversation with Edith Mallory, kept rising and looking out the window.

"What are you watching for?" she asked.

"Fog," he replied.

She shuddered. "Do you think he will come, then?" she asked.

"Perhaps he will, perhaps not."

She left Lawson at midnight; and the chemist, kissing her good night, went to take up his vigil in the library, which faced the rear of the house. He sat in the darkness, smoking cigarets. While he had not slept that day, he was used to irregular hours through his laboratory research, which kept him up for two or three days and nights at a time.

In the chemist's pocket was a vial of strong ammonia and an automatic pistol.

The great house was still. A little breeze rippled the trees outside. The night was lit with stars; and a small slice of moon was dropping behind the tree tops. Lawson sat ruminating upon the radium theft. While he had recovered the missing bromide for Mallory, the assassin who had planned such a frightful death for the Radium King was still at large. To allow such a man, with such hatred as he had shown, to go free, would mean that Mallory would never be safe.

Moran, the detective, had done his best. His shadows and investigators had looked up every possible person. Even Keating, the manager, had been carefully checked. But no success had come.

There was a chime clock in the library, and it struck one, then half-past. Two o'clock; and still the chemist sat in the great armchair, staring out into the night, scarcely moving except to light a cigaret or throw one away.

The evening papers had carried a front-page story about the recovery of Byfield Mallory. Lawson had seen them.

One, two, three! The chimes spoke again. All was quiet, save for the faint sound of the breeze in the trees. Then, a tap-tap on the window near Lawson. The chemist rose silently, and approached the glass. Outside, he saw the shadow of a man.

The window, left open by the chemist a couple of inches at the bottom for just such a contingency, served as a warning signal, by the tap on the glass, and as a speaking-hole.

"It's Ulman," whispered the man outside: "Someone has just climbed the balcony and is entering the bedroom where Mr. Mallory formerly was. What shall we do?"

"Was he alone?"

"Yes."

"Collect your men and be ready under the balcony when I throw on the room lights."

"Right."

Lawson, his heart beating swiftly for he was sure that he was about to trap the unknown assassin, the thief who had blown up the factory and stolen the radium—ran out into the main hall and up the carpeted stairs. A dim night-light burned in the upper hall. Lawson carefully extinguished it; then crept on his hands and knees along the corridor, to the door of the radium room.

He lay before the door, his ear pressed against the crack at the bottom.

The Demon

SILENCE greeted him at first—dead silence. Then he heard a faint scratching noise; and a beam of light, evidently from a flash, lit the crack for a moment.

Lawson allowed the intruder several minutes. He wished to catch the man red-handed, with the radium bromide in his possession.

At last, the time had come. The chemist, drawing his pistol, placed his hand on the doorknob. He turned it slowly; he had, among other things, oiled it carefully during the afternoon. The door opened an inch, then two inches; and Lawson looked in.

A dark figure, fantastically clad, was bending over the bed, so intent upon it that Lawson's opening of the door had not been heard. The flashlight had been extinguished. The intruder held something in his hand, however; and, as he worked, Lawson saw tiny flashes in the darkness.

A strange glow illuminated the object in the marauder's hand. "Zinc-sulphide screen," said the chemist's brain, and he was jubilant in one way; for he had known that it was a man familiar with chemistry and radium who had been attempting to torture Mallory to death. But his brow was knit.

Lawson waited. The intruder, whose vague form was black in the dark room, put down his screen and began to rummage in the mattress.

"Ah!" The chemist sighed relievedly. He had been puzzled for a moment by the screen. But he saw the man in the room investigating the mattress. The flashlight gleamed, on the glass of one of the small tubes.

Lawson put his hand around the corner, snapping his flashlight.

"Throw up your hands!" he ordered sternly, leveling his automatic.

A bizarre figure confronted him. A black gown of dull sheen, a black hood of the same material, and goggles gave the man a horrible appearance of unreality; he seemed like some frightful demon from a mad house. On his hands were black gauntlets.

But to Lawson, the figure was quite natural. It was the dress of a radium chemist; a lead-rubber dress made to protect the skin from the rays, when lead screens were not available.

"I've got you," said Lawson quietly: "Take off your hood, and let me see your face." The intruder did not move. He stood, frozen. "Take off your hood," ordered Lawson again.

The figure stood, like a statue: Suddenly, a noise behind Lawson caused the chemist to turn his head for an instant. As he did so, the black figure made a sudden backward move. A scream rent the air, and then a dull thud reached the frantic Lawson's ears, for he had realized that his sweetheart was behind him.

She had fallen, fainting at the sight of the intruder. The black-clad man dove, headfirst, through the window; as Lawson fired once after him, breaking the upper pane.

The chemist raced to the window. The intruder, his clothing crackling, was dropping to the lawn.

"Ulman, Harte, Simmons!" shouted Lawson.

The shadows were at hand. Lawson, stretching out the window, saw several dark figures leap on the neck of the fugitive.

"Bring him inside!" he ordered.

He hurried back to the prostrate form of Edith Mallory. He raised her head and kissed her. She opened her eyes a moment later.

"Oh, Young! Are you all right? I was afraid for you, I could not sleep. I came to see if you were still alive, and saw that frightful thing staring at me."

"They are only clothes used sometimes by research workers handling radium elements," he explained: "Come, the shadows outside have captured him. Hadn't you better return to your room?"

"No, no. Let me go with you."

"Very well. Come along."

Lawson went downstairs. He opened the front door, and met Ulman, Harte, Simmons and Wright, the four shadows, as well as the lodge-keeper of the estate. Also, two other detectives greeted the chemist's eyes.

"Here he is," said Ulman. "We got him."

They pushed the prisoner into the lighted hall. And, as Lawson and Edith Mallory looked at him, with his hood jerked off by the detectives, they exclaimed in surprise.

It was Charles Sommers!

"Sommers! So it was you, after all!"

The two extra detectives were the shadows who had been put on the trail of the young research chemist by Moran.

"We've been following him right along, Mr. Lawson," said Brown, one of them: "He came out here tonight, with a suitcase. He puts on this black suit and sneaks into the estate by a side gate. We trailed him up here; connected with Harte and Ulman, and they told us you had just gone upstairs to trap him. So we were ready for him if he came down. This is his first suspicious move."

"Good, you've got him. Bring him in here."

Lawson, with Edith, and the whole troop of guards, went into the library, where the chemist put on the lights, and seated the prisoner in a chair.

"Well, Sommers. What have you got to say for yourself!"

Sommers shrugged. "What is there to say?" he said: "If I tell you the truth, you'll laugh at me."-

"No, no. Confess, for you've been caught red-handed."

End of First Installment

---

RADIUM fulfills a great purpose in science, particularly that branch devoted to the physical well-being of mankind. Its rays may be rays of healing, of relief from agonizing cancer, of life.

In the hands of a criminal, however, these beneficent rays may be rays, not of life, but of death. Mr. Curry's development of this fact will expose to our readers the marvellous advances that have been and are being made in scientific-laboratories. It is difficult to credit the infinite possibilities that Mr. Curry touches upon in this story, but he deals scientifically and logically with actual facts, and withal has written an exciting mystery tale.

---

WHAT HAS GONE BEFORE

Young Lawson is investigating a mysterious explosion at the Malloradium Company's plant, where radium is produced from carnotite ore. He is assisted by his friend Detective Moran. Lawson meets Edith, daughter of Mallory, owner of the factory, and falls in love with her.

Mallory feels he is being persecuted by some unknown enemy. He suspects Sommers, a chemist in his employ, who discovered a secret process in die isolation of radium. Mallory is attacked by a strange disease. Lawson suspects radium poisoning. He watches Mallory's house and surprises a lead-protected figure putting radium under the mattress of a bed. Sommers is found near the house and is accused... Now read on from here.

CHAPTER X
Sommer's Story

SOMMERS, after some minutes of argument on the part of Lawson and the detectives, consented to talk.

"You may not believe me," he said, "but I will tell you the whole story. I discovered the process which goes under the name of Mallory's, and which he simply took from me without giving me any compensation. It made me angry. I had nothing else to do, however, and I have a wife to support. So that I did not dare to quit, even if my contract had not held me. While I had no legal claim on any discoveries I made while working for Mallory, still, I should have been given something for my work."

"That's true enough," said Lawson sternly, "But the action of Mallory, in not giving you a bonus for your process, does not excuse you for trying to torture him to death with his own radium. And the blowing up of the plant makes you a murderer; for two watchmen were killed."

Sommers turned pale. "I — I had nothing to do with the catastrophe, I swear it," he cried: "When I heard the plant had been blown up, I was utterly amazed.' I can prove I was not out that night, nowhere near the plant, in fact. I had nothing to do with the explosion, or with the stealing of the radium."

"But you knew the radium was gone, for you cornered the Beige Company's ten grams and forced Mallory to pay through the nose."

"I at first thought Keating must find the radium in the ruins. But then, I had a mysterious telephone call. It sounded like a negro's voice. Whoever it was told me that if I wished to make money out of Mallory, I could do so by obtaining an option on the Beige Company's ten grams. I tried to find out who called me, but I could not. The call started me to thinking. I was angry at Mallory for having treated me to way he did. I finally scraped together all my savings and my wife's money—for I was aware of the forfeit money Mallory had up—and obtained the radium from Leopold. I was taking a chance, I knew, for if Keating should find the radium in the ruins, I would lose my rent money on the radium. But it turned out as the man on the phone had promised. Mallory was forced to pay me fifty thousand dollars, and I was glad. It seemed only just compensation for my work."

"And you came here tonight for what reason?"

Sommers put out his hands in a gesture of despair. "It sounds like a fairy story," he said, "but this same person called me again this evening. 'There is a reward of $25,000 for the recovery of the radium stolen from Mallory,' said the voice. 'You can get the reward by finding it.' 'Who are you?' I asked. 'Never mind,' said the voice. 'You cannot trace me. But you know that Mallory has been burned by radium. It was present in his bedroom. Probably you will find it there if you go right away.'

"I did not want to go. I was afraid. 'How do I know this is not a trap?' I asked. 'Did you not follow my advice to your own advantage before?' asked the person. I had to admit he was right. And his next words frightened me. 'The police suspect you of stealing the radium,' he said. 'They will try to make you the thief. But if you discover the radium which must be somewhere in Mallory's former room, you will be cleared. Look in the mattress.'

"I had read the papers, and knew that Mr. Mallory had bad radium burns. I also had read that day that he had been moved from his former room to another, and was getting better. And the idea of twenty-five thousand dollars more, for finding the radium, acted strongly to bring me out here; that, and the wish to clear myself. I had not thought I would be suspected of the crime of blowin up the plant. What I had done was simply a sharp trick to my mind, and I said nothing about the phone calls, even to my wife. I had a suit of lead rubber clothes which I sometimes make use of. I have it on now. I brought a zinc sulphide screen to identify the radium if I found it. And I did find it. It is hidden upstairs in the mattress of Mallory's former room."

"How did you know where he had been sleeping?" asked Lawson.

"I was informed by the voice over the phone. It was a negro speaking, I am sure."

The detectives, the girl, and the chemist, had listened carefully to the strange tale of Sommers.

Detective Harte grinned behind his hand at his partner Ulman. "Some alibi," he said audibly.

But Lawson's brow was wrinkled heavily. Bizarre as the tale sounded, Sommers' voice had a ring of the truth in it.

"Fifty a week!" exclaimed Sommers, indignantly. "Think of it! After I had placed Mallory in a position to fight the foreign monopoly!"

"Father told me about it," said the girl softly. "He had been intending to do something for you he said. I made him promise he would reward you."

Sommers shrugged. "That's the reason why I worked that trick on him," he said. "I spent a year, night and day, getting my process perfected."

Detective Brown was standing by the window. He had heard the prisoner's explanation of his presence there, with an expression of incredulity. He chanced to turn and look out into the night. He pressed his face against the glass.

"Whew!" he exclaimed, aloud. "Some fog coming up, boys. Lucky we got our bird when we did."

"What?" screamed Lawson, turning suddenly. "Fog, did you say?"

"Yes, sir. What of it?"

The company was utterly flabbergasted to see the chemist tear out of the library. They heard him running upstairs, and then his feet in the corridors.

Edith Mallory was the first to follow him. "Young," she called after him, "what is it?"

"Stay here and watch the prisoner, Brown," ordered Ulman. "Come on, Harte, something's up."

The detectives ran up the stairs, after Lawson. Edith Mallory was already at the top.

Inside the lighted chamber, they found the frantic Lawson staring at the mattress of the bed. It was ripped to pieces, completely, and balls of felt were strewn in confusion nearby.

Lawson turned to them. 'The radium's gone," he cried. "It's been stolen while we fooled away our time with Sommers downstairs. All guards are inside, and the thief has had a clear road. Hurry out, Ulman, and see if you can find anyone."

No Trail

THE fog had cleared of itself. Lawson had searched for traces of intruders outside and in, but though he found plenty of signs such as footprints under the window there was nothing which would help him to locate the thieves. The ground underneath the windows of the room where the radium had been was cut up by many feet, the footprints of Sommers and the detectives being mixed indiscriminately in the grass. But the gravel paths did not hold footprints.

"What a fool I am not to have placed the radium safely in a lead box and kept it with me, groaned Lawson to Edith. "Darling, its gone again."

"Don't care," she said, soothingly. "You're wonderful, Young."

"No, I'm a fool! What a trick, what a trick!"

"Do you think Mr. Sommers was part of it?" she asked.

"I don't know. He may have had accomplices outside, who stole the radium while he kept us occupied. But then again, if his story about the phone calls is true, do you not see it all fits in with this? To get a free path, the person called Sommers and sent him to be taken in our trap, thus leaving the coast clear for the second theft of the radium. It was cleverly done, but I should have been more careful. Edith, the assassin might even have entered your father's room and killed him at his ease, for the guards were inside. "What a fool I am!"

Mallory was asleep. The nurse was in the room with him, and had heard noises outside, but had taken them for the detectives, wince she knew the estate was under guard.

The butler, John, appeared, fully clad, sleep in his eyes, but looking very dignified. He approached Edith Mallory, as she spoke with Lawson in the corridor.

"Madam," he said, "the servants are greatly alarmed by the strange happenings and noises on the estate and even within the house. Can you give me an explanation of them?"

"Why yes, John. Someone has been attempting to take father's life. Tonight a man was captured, but there are more at large. That is all."

John shook his head sadly. "I do not know if we can remain longer here," he said.

Edith smiled. "I don't think you are in any personal danger, you or any of the servants."

* * * * * *

John the butler was unconvinced. Lawson was not at all surprised when Edith Mallory told him next morning that all the staff, following John, had resigned.

"I can easily get another staff, by calling the agency," said Edith. "I will do so. at once."

"Yes, of course. I must go into town this morning, dear, to see Moran."

Brown and his partner Williams had taken the prisoner Sommers in to headquarters. Moran would have the chemist there, and would be endeavoring to get a confession from him. Lawson wished to see his friend.

Shadows were still on the estate, four having come out to relieve the night men.

Lawson reached headquarters and found Moran closeted with Charles Sommers.

"He repeated the same thing over and over," Moran told Lawson. "The story he told last night. Won't come across. You said it was a chemist we were fighting and this looks like our man to me. He probably had accomplices outside who came in and stole that radium when the coast was clear."

Moran, it is not at all certain that Sommers is not telling the truth? I wish he was our man, so that we could solve the case and set Mallory free from danger. But if what Summers says is true, then there are other more powerful enemies with which we have to deal."

You're right there. His accomplices, if he did it, are still loose. They are probably as dangerous as the master criminal."

"Yes. It is obvious someone wants to kill Mallory by degrees, to torture him for revenge. It is a chemist, and a man with a deep enough hatred to go to great personal danger to gain his end."

Moran thought for some time. Sommers, returned to his cell had been obdurate.

"Listen, Lawson. If these birds, whoever they are, want to hurt Mallory, there's a chance they might get his goat by harming his daughter!"

Lawson nodded. "Yes. Moran, I must stay close to her, to protect her. Please keep your men outside the mansion."

Lawson, before returning to the Mallory estate, went and saw Keating at the latter's home. The manager was still in Mallory's pay, and was resting.

"How's the boss? Better, I hope."

"Yes, you know, I found the radium?"

"Good heavens! Where?"

"In Mallory's bed. Someone put it there to kill him."

The amazed Keating listened to the chemist's story, of the finding of the radium.

Well—I'm glad you've got it. Now I can get busy and sell some of it. The boss's affairs are in busy shape. I'll get Leopold and Tollerman and see if they will still buy ten grams." The manager reached for the phone.

"Wait. The radium is gone again."

And Lawson told Keating of the capture of Sommers.

"Sommers! I thought it was he! Some accomplices must have come in after you were out of the way, and pinched the radium."

"I don't see why he did not try to steal it himself," said Lawson.

"The chemist gave Keating Sommers' explanation. "Do you know any negro who might have made such a call?"

"No, good heavens, Lawson! What a cock-and-bull story! It was Sommers all along, I'll swear."

"Will you? Then who put the sodium chloride in the ruins?"

Keating flushed. "Probably one of his accomplices. Sure, Sommers had it done to make a fool out of me."

Keating was unable to assist the chemist in his inquiry. He knew of no negro who would wish to commit of be capable of performing such crimes against Mallory.

CHAPTER XI
The Unseen Enemy

IT was dark when Young Lawson got back to the Mallory estate. He had made some purchases during the afternoon, this and a visit to his laboratory taking up his time.

The girl opened the door for him and greeted him joyfully. "I've missed you terribly," she said "I'm getting so I have to have you here every minute!"

"How is your father?"

"All right, much better, Dr. Morse says. He had broth and toast for his supper. The ulcers are closing."

"That's good," said Lawson, breathing a sigh of relief. "Have the new servants come?"

"Yes. They came from three different agencies, and do not all know each other yet. The butler's name is David."

Dinner was served to the two in the big dining room. Lawson, in spite of the strain under which he had been living, was almost perfectly happy, with the beautiful girl seated opposite him at the table.

But a shadow of dread was over him. Moran's words, "Suppose they decide to harm Miss Mallory?" kept recurring to him.

They finished dinner, and went to the library to talk over their future life together. Lawson produced a diamond ring he had bought that afternoon, and slipped it on her finger. She kissed him joyfully."

"I'm so happy," she cried. "You make me happy, Young, just being near me. Father will get well, I'm sure, and I don't care if we aren't rich. We'll always be happy together, won't we?"

The chimes struck nine. Lawson rose. "I wish to go outside for a few minutes," he said. "I've got some stuff I want to plant—what is it, dear?"

Lawson's heart suddenly leaped madly. He felt strangled. The girl's face had turned pale, and she was looking at her lover with eyes which were rapidly growing red.

"Young—it's close in here—my throat burns—"

Lawson, with a cry, seized her in his arms. He was frantic. He felt his brain growing dim.

"Put up the window, put up the window," gasped the girl.

"No, no!"

The chemist, carrying the semi-conscious girl, limp now in his arms, rushed out into the great hall. The air was a little better there, but still that sensation of utter helplessness was on him.

He knew at once what had occurred; by the sensations and odor he recognized, even as his eyes failed him, that they were being overcome by a tear gas. His eyes smarted, and his nostrils burned. But he managed to place the girl gently on the floor, where the air was a trifle clearer.

If he could have got to his room and obtained some of his chemicals, he might have contrived some sort of protection; but the attack was so sudden he was left defenseless.

He lay, half unconscious, stifling. The gas permeated the room. The tear gas was a brominated xylene, probably; he knew how to fight such a substance, but the preparation of a gas mask would have taken time and he was caught unawares. But he realized, too, that the tear gas was not highly toxic.

It was an hour before Lawson, eyes burning, weak from the effects of the gas, managed to struggle to his feet. He raised a window and sniffed. The little breeze had carried away what remained of the gas. He then opened more windows, and obtaining water, bathed Edith Mallory's face and eyes tenderly until she regained consciousness.

"Darling," he murmured.

She put her arms out to him. He kissed her wet face. "We're all right," he said soothingly. "It was only tear gas."

She was able to sit up in a chair. Lawson called from an open window, for Ulman and Harte. But no answer came to him.

He was afraid, for Edith. He did not dare to leave her, to investigate. But soon she was able to stand up, and together they went up the stairs, to see if her father was safe.

The door to Mallory's chamber was locked. No reply was given to their frantic knocks. Finally Lawson placed his shoulder against the door, and broke the lock.

Chloroform

THE room was lighted. Inside, was a faint, familiar smell, and the chemist's face, red from his exertions, was deeply lined with worry.

The great bed set in the center of the room was empty. Mallory was gone.

"Father," cried the girl. "Father!"

But no answer came to them. On the floor, in a corner, they discovered the nurse, unconscious.

"Chloroform, and the tear gas, both," said Lawson, almost to himself.

The window was open. The fresh air was blowing in, clearing the atmosphere.

"Oh, my God!"

The nurse was coming to. Lawson, bending over her, helped Edith Mallory revive the woman, a dark young lady of thirty who had been the night nurse. The nurse had developed, from her work at Mallory's bedside in the first room, a radium burn which Dr. Morse was treating. But she had stuck at her post.

Soon she was able to talk. "I—I was sitting in my chair, reading by the bed, with my back to the window. It was open a little, for fresh air. Mr. Mallory was peacefully sleeping.

"It seemed close to me; I began to cough, and I thought I would open the window a little more. Then I smelled chloroform! I ran to the window, to throw it up, and a horrible face was looking in at me, and was spraying chloroform into the room! I tried to scream but my breath was gone. All I can remember now, is that the window was thrown up from outside, the dreadful face came at me, and I lost consciousness."

"Perhaps the face simply wore a gas mask," said Lawson.

"Yes, of course. But I was frightened out of my wits, anyway. Is Mr. Mallory all right? What do you suppose was the object of this?"

"Mr. Mallory has been kidnapped," said Lawson "The object of the gas, which was tear gas, brominated xylene probably, and the chloroform spray, was to put you and the guards out of the way, and capture Mr. Mallory. But come, we must hurry. Edith, you must stay close by my side."

The cries of Lawson brought the lodge keeper, who said he had a whiff of the tear gas bug had not been badly affected.

Under Mallory's window, they found the marks of a ladder. Many feet had cut up the ground, but again the marauders had used the gravel paths in their escape, and there was no trail to follow. Malory had been bodily carried off.

It took a full hour to find the four shadows who had been set outside the mansion. Ulman and Harte were located, bound and gagged, under some hedge near their post; the other two were found tied up and gagged, on the other side of the house.

The detectives were fully conscious.

"The tear gas came on us suddenly, said Harte, ashamed of himself at having been taken, "but it didn't get us very badly. However, we were coughing and choking, wondering what it was all about when we were jumped by several men in gas masks and tied up."

The others repeated Harte's story. "I'd better call Moran," said Lawson. We must have more men."

The chemist searched for further traces, and cursed himself roundly.

"Edith," he said, "I want you to go to your room and stay there. You need rest, dear. I will have your room guarded, and will watch myself. We'll find your father. They can't have carried him far."

"Perhaps they had a car on the outskirts of the estate," said the girl.

Well, then we'll find the car. Someone may have seen it."

But though Lawson spoke optimistically, he was by no means certain he could fulfill his promise. The kidnappers and assassins had shown themselves to be versatile enough to overcome every obstacle in their path.

When the girl had gone to her room, which was at the front of the house, Lawson called the four shadows together. "Stand under her window with drawn guns," he said sternly. Ulman, you go to her door and stay there. Do not let anyone get near her, do you understand?"

"Yes, sir."

Harte and his two comrades accompanied the chemist to the turf beneath Edith Mallory's window. The chemist obtained a large bag of white substance, and when he was under the girl's room, he began to sprinkle this about.

"What's that?" asked Haute curiously.

Potassium iodide," answered Lawson. He was not pleased with the way the shadows had acquitted themselves, though they were scarcely to blame for what had happened.

"What for?"

"Never mind. You boys are not to get your feet in it, do you understand?"

"All right, sir. It looks like common salt, to me."

"Yes, but it's not. Now, you keep out of it, do you understand?"

Yes, sir."

Lawson had practically covered the turf with the white salt.

He had planned to do this same thing under Mallory's window, and that night, too. But the kidnappers had forestalled him.

"New, I'm going in to call Moran, and have more men sent out," he said. "Watch carefully, Harte." "Yes, sir."

CHAPTER XII
The Attack

IT was eleven P.M. when Lawson finished his preparations. To protect the girl was his main object, for his heart was cold with dread that the marauders, having accomplished their first kidnapping, might seek to injure Mallory further through his daughter.

The sudden display of force by the invisible enemy had shocked the chemist; he had thought he had to do with but one or two men. But now, it appeared that whoever wished horrible destruction on the Radium King had more resources at hand than Lawson or Moran had guessed.

More and more, Lawson had abandoned the idea that Charles Sommers was at the bottom of the crimes. There was someone watching the mansion carefully, planning each devilish move with a cunning that had outwitted every precaution of Moran and Lawson.

As Lawson started into the library of the mansion, he had three objects in mind. The first was to call Detective Moran and order that worthy to come at once with a large force of men, for the purpose of organized pursuit of the kidnappers—if traces could be found—and also for protection. Instinct warned the chemist that he might not have seen the last of the intruders. Second, Lawson intended awakening the new butler and footmen—he wondered why they had not appeared before—to press them into service as extra guards, and third, the chemist was going to plant himself outside the door of Edith Mallory's room, and stand, gun m hand, alert to every sound, until Moran came.

A light step sounded in the corridor behind Lawson. The chemist his nerves ragged, turned swiftly. A tall man, in livery, stood before him.

Is anything wrong, sir?"

"Are you one of the footmen?"

"Yes, sir. Can I be of assistance?"

"Yes," snapped Lawson. "Wake up the butler and other men, and arm yourselves. You must remain on guard until I can get more police out here. Do you understand?"

"Yes, sir."

The man turned and went down the hall. Lawson went into the library and started for the telephone, set on a stand in a corner.

The chemist's forehead was knit with wrinkles, lines of worry. He was intent on his plans; he spoke to himself, his lips moved in his abstraction.

He did not see or hear the silent creature who slipped in the door, creeping up behind him.

It was the man in livery. The fellow slid across the heavy carpet of the library, his footfalls deadened now. In his hand he held a blackjack, and he was within two feet of Lawson before the chemist, who was reaching for the phone, sensed his presence.

The blackjack rose, and fell with a dull thud on Lawson's head.

* * * *

SILENCE greeted the chemist as he opened his eyes and stared, uncomprehendingly for a few moments, about the library. His head throbbed like a dynamo; a lump the size of an egg was raised and his scalp felt tight.

"Jiminey," he mumbled, rubbing his hand over the sore spot.

He was lying on the floor. A few inches from his hand was the telephone which he had been about to use.

"Help," he called feebly, "help!"

He waited, weak and sick. There was no answer to his cry.

"I must get up," he whispered. "I must! Edith!"

He managed to pull the stand over, and he seized the phone as it fell on the floor, and gave the operator a number. He was connected with headquarters.

"Detective Moran has gone home. What can we do for you?"

"Send a squad of men out here at once. This is Young Lawson, and I'm at the Mallory estate. There's been a raid out here, and we need help."

After a few more instructions, the chemist hung up, the assistance he had ordered promised. He felt a little stronger, and was able to sit up. He called Moran's home, and presently the detective himself answered.

"Hello ? What's up?"

"It's Lawson. Moran, Mallory has been kidnapped. An attack has been made tonight. Come at once. I've called H.Q., and they're sending men. Hurry."

"I'll be there in twenty minutes."

Lawson rose unsteadily to his feet. He was filled with a dread foreboding. He called out for help again as he advanced along the hall towards the stairs.

The servants' wing was way off at the farther end of the house. But Lawson's first object was to find his sweetheart.

He knew that what he feared had come upon him when he saw the prostrate figure of Ulman lying outside Edith Mallory's door. The detective was bleeding from a serious bullet wound in the thigh, and he was gagged and tied for the second time that night. Signs of a furious struggle were visible. Ulman had done his best to keep his trust.

But the frantic chemist leaped towards the closed door of the bedroom. "Edith," he cried. "Edith!" He banged furiously on the door. There was no answer,

The chemist pushed the door in. The light was burning in the room. But it was empty. The window was open.

Lawson ran swiftly along the corridors. He reached the servants' wing, and called lustily.

At last, he was answered by a frightened man's voice from within the barred doors.

"Is that you, Dr. Lawson?"

"Yes. Open the door."

A stout, middle-aged man, whose face was normally red as a beet but was now pale as sugar, opened the door, and stood, trembling violently, his teeth chattering, within the opening. He was clad in pajamas and a blanket.

"Well, David," said Lawson, recognizing the new butler, "where's the rest of the servants? Did you hear nothing? Why haven't you come out?"

"Oh, sir! We did hear noises earlier in the night, and the footmen, Thomas and Francis, got up to investigate. I got up, also. But before we were able to find out what was the matter—there was something in the air which hurt our eyes and lungs, too—two gigantic niggers came in the window—my window, sir—and leveled revolvers at us! We had gathered together in our hall, you see. It's our first night here, and we're not familiar with things."

"Two negroes came in?"

"Yes, sir. They were masked with black hoods, but their black hands betrayed them. They said they would kill the first one of us who dared to move out of our quarters! We heard you calling for help, but we did not dare to go out. We feared they might come back and kill us."

The butler was regaining a little of his composure. He had made a fool of himself before his subordinates, and he wished to regain some dignity. He drew himself up, looking as dignified as he possibly could under the circumstances. The maids, cowering nearby, and stalwart footmen, waited and watched.

"Sir," said the butler, "we have scarcely been in this household twelve hours, but I assure you we have all come to the conclusion that the best thing for us to do is to leave at once! We do not wish wait until morning, we will go right away. I shall, for one. Such a place is not for us!"

"Why haven't you come out before this? cried Lawson testily. "Do you know that the marauders came back and that you might have helped us fight them off if you had been on duty?"

The Last Lap

"WE are aware, sir," said the butler, "that the murderers returned. The negroes again appeared, and we realized we had done well not to budge from our quarters. They stood over us with great pistols, laughing at our natural terror. There was a tall man with them, masked also, who took Francis's livery and put it on. We heard shots in the house and outside and when I tell you sir, that, we did not come here to engage in rough-and-tumble battles, sir, I tell you the truth. We were kept under guard until half an hour ago. The negroes then left, telling us not to move out or we would regret it."

Lawson shrugged impatiently. "Cowards," he growled, and turned on his heel.

His gun remained within his pocket. It had not been taken from him. He grasped it in his hand, and taking a flashlight, went out into the night.

The ground beneath Edith Mallory's windows was trampled to mud. Clotted blood, dark red on the ground, whitened by the substance which Lawson had placed there, showed that the outside guards had been fighting.

Harte lay nearby, dead, a revolver clutched in his hand. The other two shadows, both with several bullet wounds in them, lay in the clumps of hedge, bound and gagged, suffering intense agonies. Lawson unbound them, and carried them into the mansion and phoned for ambulances. He attended to Ulman as best he could placing the detective, who was conscious but unable to speak, on a bed upstairs.

While he was at this work, he heard motors come up the front drive, and pull up. Then he was aware Moran's shouts.

"Lawson!"

The chemist ran downstairs and let the detective in. Moran had twenty men with him.

We found the lodgekeeper knocked on the head down the drive. said Moran. "What's up?" Lawson gave Moran a swift account of the nights happenings.

We must hurry, Moran," said the chemist. "Have a couple of your men left here, to care for the wounded. I have sent for ambulances.

"Well—what shall we do now?" asked Moran.

We must search for the kidnappers, at once," said Lawson.

"Sure. But if they used the gravel paths, their trails covered." "Moran," said Lawson, "if my theory is correct, the kidnappers should be established not far from the estate. The have shown this by the short time they took to dispose of Mallory and to return for Miss Mallory."

"Maybe they had cars," suggested the detective.

"That is possible. If so, we're lost. Otherwise, we have a chance. Send your men outside, to see if they can pick up any trail. I'll be back in a moment."

CHAPTER XIII
The Chemical Trail

LAWSON his head still sore and aching, returned to the detective's side before the minute he had promised had elapsed. In his hand, the chemist held a glass bottle filled with a colorless liquid, and with a bulb atomiser attached so that the liquid could be sprayed. From his pocket stuck another.

"Come, Moran. I am praying I am right, and that whoever has accomplished all these crimes against Mallory is living nearby, perhaps not more than half a mile away. If so, I can find him."

Moran had battery searchlights in his cars, and he sent two men for them at Lawson's order. Four were left at the mansion, and the rest, grouped behind Moran and Lawson outside Edith Mallory's windows, listened to instructions.

"Now," said the chemist, his voice tense, trying to control the fear which he had for the safety of his sweetheart, "I want every man to use his eyes. Do you see this white salt upon the ground?"

The searchlights played on it. Though well-trampled into the damp earth, the potassium iodide was quite visible.

"Watch closely for bits of this," said Lawson. "Keep your own feet out of this mess here. The kidnappers have traveled on the gravel paths."

It was possible to trail the marauders to the gravel paths. There the trail seemed lost. But the detectives, spread out in a long line, with flashlights and searchlights, went on.

"Here's something looks like it might be a bit of that stuff," said Moran.

Lawson ran to the detective's side. He sprayed a bit of the liquid onto the pinch of dirty white salt. Moran, watching, saw it turn brilliant yellow.

"For the love of heaven," exclaimed the detective. "What's that?"

"The salt is Potassium iodide," said Lawson. The solution I have in the bottle is lead acetate. The product is yellow lead iodide. See, I'm sure that is it!" He took the other spray from his pocket, and shot a few drops of liquid onto the yellow specks. They slowly turned from yellow to scarlet. "Mercuric chloride in this bottle," said Lawson. Gives scarlet mercuric iodide. Hurry!"

On they went and every now and then, a detective would cry out that he had found what seemed to be a bit of the salt. Lawson sprayed each one, and while he was disappointed several times and there was no color change, they were able to go on for some hundreds of yards.

Then the trial failed. They had gone for over a hundred yards without finding a bit of the salt. Magnifying glasses, provided by Lawson, for Moran and himself, brought none to light.

"God help us," groaned Lawson. "I thought it would hold up longer than this!"

They returned sadly along the gravel path they had been following, for no signs aided them. Lawson, looking carefully on each side, gave a cry.

"Look, Moran! This path we're on runs within two feet of that other one at this point! It would be possible to step across the grass without leaving a mark."

And Lawson demonstrated his statement. He hurried along the new path, going from the mansion, and a few moments later stooped and examined the path by the aid of his flash and glass.

It was only a speck, but the color change worked. "We're on them again," cried Lawson.

On they went, the trail growing slimmer and slimmer, resting upon a few specks of white salt. They finally reached the edge of the broad estate, and found themselves on a side road to the east of the mansion, a quarter of a mile from the main road.

"What d'you suppose that mark is?" asked Moran, pointing to a long, flat impression in the soft earth which separated the gravel path from the hard far road.

"The mark of a board," said Lawson, examining it. "Yes, Moran, they've simply laid a board there, to walk across and cover their footprints."

The Resources of Science

"WHICH way now?" asked Moran.

The chemist found bits of gravel on the road by the aid of his glass, and he sprayed several. He got a slight color change, and the whole troop ran along the tar road.

There were houses within a few blocks of them. The searchlights illuminated the black road. Two or three specks of the salt were found and answered to the test.

Then the trail failed again. They had missed a turn-off somewhere. They retraced their steps.

The houses were in blocks, but here and there was one which was set off from its neighbors.

Lawson stood, agony in his heart. His chemical trail had failed him now.

"Moran, I am sure they must be about here somewhere. Yes, if they had had cars, they would have had them ready at the edge of the estate. We must now use our imaginations and trust to luck. They have evidently turned off, down one of these side streets. Let's send men along these three, from where we have lost the trail, and see what we can find."

The men were split into three groups. Moran had charge of one, Lawson the second, and a lieutenant of detectives a third.

Lawson led the way down the side street, which was paved. The houses were dark; it was two A.M., and few people were awake.

A small green house, with white shutters, showed a light on the second floor, the block shades being drawn. Lawson hesitated before it, all of his troop listening carefully.

No sounds reached their ears. "Climb up and see if you can look in," ordered Lawson of one of the men.

The spy was hoisted to the roof of the porch. He peeked under the curtains of the lighted room. A moment later, he crept away and dropped to the ground.

"There's a sick person there," he whispered. "I saw a nurse asleep in a chair and a grey-haired woman in bed."

They carried on to the end of the block. There they waited for Moran and the other troop.

* * * * * *

Moran came hurrying to Lawson's side.

"Listen, one of the boys has just found what he thinks may be a trace of that white stuff. Bring your spray up here."

Lawson, followed by his troop, ran after the detective. In the center of the block, Moran's other men were collected. There was a house nearby set off by itself among some trees in a large lot. No lights showed in it; but the searchlights showed a few specks of white upon the sidewalk.

Lawson sprayed the specks, but they did not turn color. "No luck," he groaned. "It's just some sort of white powder."

"Say, why not take a chance on this joint, said Moran, indicating the house among the trees, "It's our last bet. I investigated three places that were burning lights, but we got nothing suspicious."

The third troop had joined them. They had found nothing.

"Come on, then," said Lawson.

They went quietly along the driveway the house. No sounds greeted their ears.

The men were distributed about the place to look for clues. Lawson and Moran crept to the front steps.

"Someone's wiped his feet here, bottom Moran, pointing to a foot-scraper on the bottom step.

Lawson looked through his glass at the scraper. He tried his spray on it. The yellow color answered and Lawson's heart leaped rapidly.

"This is the place, Moran," he whispered, "the chemical trail has been successful!"

All lights were put out. The house was silent as the tomb. But then, Moran and Lawson, creeping around the place, found a faint speck of light coming from one of the basement windows. All the other windows showed black, and as the two men inspected them at closer range, it was evident they were covered inside with some sort of black cloth. But a small fault in the material in the one place betrayed the light inside.

The detectives, with drawn guns, were set closely in a ring about the suspected house. Moran ana Lawson keeping together, stepped quietly to the front door.

It was locked, as they had expected. All the windows along the porch were also fastened.

The Fight

"WE'D better enter by the cellar," whispered Moran. A click nearby sounded through the night. The front door was opening. Lawson and Moran drew back into the shadows. A man stepped from the door, his coat muffling his face.

But the figure was familiar to Lawson. It was, he was sure, the man who had posed as footman and who had struck him down in the library of the Mallory home.

Lawson pressed Moran's arm. The big detective rose up from the blackness of the night and leaped on the man, obtaining a strangle hold which broke off all cries.

A dull thud, as the two bodies struck the porch, and then Lawson, clubbing his pistol, brought it down on the enemy's head. The man ceased to struggle.

The front door was open. Moran sprang inside, and Lawson, with several detectives, followed. The men found themselves in a dark hallway. They stood, listening for a moment: then, a cry from the rear of the house showed them they were discovered.

Several big figures ran at them, with guns. The flashlights illuminated them as came, and black skins glistened in the light, men were negroes.

The blacks began firing at once; the detectives answered. More detectives rushed into the house. Lawson slipped along the wall, and up the stairs.

The upper rooms were empty, save for furniture. Lawson exclaimed in dismay. Then he remembered the cellar, and hurried down the back-stairs.

As he reached what was the kitchen of the house, door near him opened, and tall, dark figure emerged. Lawson threw his flash on the man.

"Throw up your hands!" he ordered.

But the man, who had been on the point of slipping out into the night, made a sudden lurch forward.

Lawson fired, wounding him; then the fellow grappled with the chemist, and they fell to the floor, fighting each other in the dark. Warm blood from the man's wound bathed the chemist as he struggled to subdue the injured man. But the man did not cry out.

At last, Lawson managed to strike his assailant's head a glancing blow with the pistol. And then, Moran rushed into the room, followed by his men. They had beaten the negros and captured them.

The detective pulled on the electric light. And before him, Lawson saw the master criminal.

CHAPTER XIV
The Room of Death

A TALL, fair-haired man, with blue eyes and brown hair, with a bullet wound in his left shoulder, stared up at his captor. It was Stephen Tollerman, the executive of the Beige Company, whom Lawson had met when he had visited the offices of Dr. Leopold.

"Jumping Jupiter! Tollerman!" exclaimed the chemist.

"For the love of heaven!" said Moran.

What is the meaning of this attack?" said Tollerman, thickly. "We thought you were bandits."

"Did you?" said Moran. "Well we're not. We're from police headquarters. Where's Mr. Mallory and his daughter.

"Mr. Mallory? His daughter? They must be at home."

"Come off! We've trailed them here!"

"Bring him downstairs, Moran," ordered Lawson.

The chemist descended to the basement. He went to the room where they had discovered the speck of light filtering through the window.

It was a small room, with three small windows. The walls were lined with heavy, soundproof material.

As Lawson entered, and turned on the light, he gave a cry of joy, mingled with terror. Before him, on two broad planks which had the appearance of biers, lay Byfield Mallory and his daughter, Edith. They were separated by less than a foot. Suspended above them, on wire, were nineteen small glass tubes filled with a white salt.

The girl's face was pale as death. Her eyes were closed, and her head, mouth gagged and bound, was flung far back. Her hands and feet were tightly tied to the board.

The Radium King, tied likewise, but able to see the sufferings of his daughter, lay with wide-open eyes, with the horror of what was worse than death in them. A man may undergo sufferings of his own with some degrees of fortitude, but to see one's child tortured is beyond endurance. Yet Mallory, powerless, sick and weak, was forced to look upon Edith as she lay within the range of the death-dealing radium rays.

Lawson leaped first to the girl. A few slashes of his knife, and the unconscious beauty was freed. Moran was loosening the bonds of Mallory.

They carried the two from the chamber of death. Lawson worked to revive Edith Mallory. The Radium King could scarcely speak, but the sight of Stephen Tollerman caused his face to contract into a frightful grimace and he raised his hand weakly and pointed straight at the tall man.

It was he," he whispered.

Moran had handcuffed the prisoner. Tollerman, glowering darkly, looked with hatred upon Mallory.

"Curse you, Mallory! I should have killed you outright, when I had the chance. But I wanted you to suffer as I have suffered. Damn your heart and soul!"

"Why have you done this terrible thing?" asked Lawson, approaching the prisoner.

Tollerman looked haughtily at the young chemist. He did not deign to answer.

But Mallory spoke, feebly. "Revenge," he hissed.

The Prisoner

EDITH MALLORY opened her eyes, and threw her arms about her lover's neck. He kissed her gently.

"Oh, Young! You're here. I knew you'd find and rescue us. It was horrible. They carried off bodily and brought me here, and tied me down in the cellar, with father."

"Do you know anything about this man?" asked Lawson, indicating Tollerman.

The girl, seeing the manacled Tollerman for the first time, shuddered.

"Oh," she cried, "it was he! Young, this is the man who had been trying to torture father to death. He spoke a great deal, while I was conscious. He hates father for something father did to him years and years ago! He knew mother, too."

Tollerman showed pain; he winced. "Yes, I knew your mother," he said, in a low voice.

"Will you talk?" asked Lawson. get the story from Mr. Mallory?"

The Radium King was trying to speak. He pointed again at his enemy. "I thought him dead!" Lawson caught the words from the feeble man's lips.

"I will talk," said Tollerman finally. "See if I have not had justification for my revenge!"

* * * *

"It is twenty-five years since I first knew Mallory," said Tollerman, in his low voice. "I was a friend of his, and I was in Colorado at the same time as he. I traveled for many miles in the bad lands, searching for valuable ores. I had met a young lady, the daughter of a wealthy ranch owner, on my peregrinations. Her name was Nora Green. I loved her. I hoped to marry her when I was wealthy. I introduced Mallory to her.

"As I said, I was after ore.

"You know, there is a terrible lack of water in the bad lands. It is necessary to carry all drinking and cooking water, especially in the parts where I was prospecting.

"Now, I had been among the first to search definitely for radium ores in the west. I was a chemist and knew the then new chemistry of radium. The first of the carnotite ores there were my find.

"Mallory had a powerful organizing ability. He thought he could get backing in the East for our work. We had a great deal of argument about the value of the ores, and I wanted to be given half of the profits, while Mallory thought that much.

"Before bringing capital into the problem, we wished to make sure of our claims, and also to obtain further specimens of the ores. We, therefore, started off on a trip to make a last survey of the country. We would be gone over a week, for it was a two-day ride to the ore lands.

"We were well-mounted, however, and knew our way. The argument between us increased; Mallory had a had temper then as he always has had. We almost came to blows about the division of future profits, for we were sure of the value of my find.

"However, we reached the place where I had found the ores. It was vast in extent, a yellowish earth which promised to yield rich uranium deposits.

"For twenty-four hours we prospected, taking samples of the ores from different sections of the hills.

"Then we started back for town. We had had much argument together, about what I should be given for my discovery. Also, there was jealousy, for Mallory had been showing attention to Nora Green, and I knew it.

"'Go to hell!' I cried at last. 'I won't ride with you!" And I spurred my horse forward, to separate from Mallory. I galloped for some distance, and then I looked round, intending to shake my fist at him. Then my horse, speeding forward, broke the upper crust of earth over a hole and he went down. If I had been riding carefully, I would have been unhurt; but my leg caught in the stirrup arid my horse fell on it, snapping it just below the thigh.

Left Alone

"OF course, the pain was terrible. But I waited for Mallory to come to me."

Tollerman, his lips set in a grim line, glared at the man he hated. "Well?" said Lawson.

"He did not come. He left me there to die. For three days I lay suffering. The pitiless sun beat down on me, and my face turned black. My canteen had been smashed and only a few swallows remained in it. They kept me alive till the evening of the third day.

"The nights were chill, the days roasted me. The horror of that is still in me. I have never recovered from it. See, the streaks of grey in my hair came then.

"My throat burned like a furnace. There as no more water. I was delirious half the time, clear-headed the rest. Finally, I felt I must kill myself. But I went mad then, and raved in the desert.

"I can remember nothing more. It was three months before I began to recover. I found that a band of roving, prospectors, looking for gold, had found me, and carried me west, to a town beyond the hills, where there was a doctor. My leg, which still pains me at times, was set there, and I was sent to a hospital in a city.

"When I was well enough to go out again, I was a shadow of my former self. But the hatred within me against the man who had left me to die so horribly was so powerful that I felt I must kill him on sight.

"I returned to the little town. I made discreet inquiries there, since I did not wish to be identified as his murderer. My long illness and the ordeal through which I had gone, had changed me so that no one recognized me. I found that Mallory had put in a claim to my ore deposits and been granted them. He had gone east, for capital. "Up to this time, my only desire had been to kill him. But then, I learned Mallory had married Nora Green, the girl I had adored, and taken her with him. It was then that I realized the extent of my hatred towards him.

"I have carried this in my heart ever since. My constitution was ruined by the terrible hardships I had undergone. My heart was broken by his having stolen Nora, and I was penniless and out of the radium company.

I vowed vengeance then. I vowed to torture Mallory as he had tortured me, by a slow death. I changed my name from James Tholl to Stephen Tollerman, and I kept out of sight. I went to Europe, then wandered into Africa. I was one of the discoverers of pitchblende ores abroad, and I have recently become rich. Some weeks ago I returned to my native land. It was a long time since I had seen Mallory, but I recalled my vow and now I was ready to carry it out. I did not wish him to see me, for fear he might recognize me. Dr. Leopold, our representative here, knows nothing of my designs against Mallory. I found my enemy grown fat and prosperous.

"I had several faithful followers, picked up in my wanderings, negroes and a Frenchman you have captured. They came with me to this country, where I set about my revenge."

"You knew Mallory had taken Charles Sommers' process?"

"Yes. And I wished to injure Mallory as much possible. I therefore, after my men and I had stolen the radium bromide and destroyed the plant, sent him to take an option on the only available ten grams on hand. Leopold had mentioned to me that Mallory had a guarantee sum placed to deliver that much radium on time. We knew, of course, that he was planning to compete with us, and knew of his orders. When I had the radium, I returned one night and placed the lead box in which it had been in the ruins, with salt in it. This was to annoy Mallory.

"I was able alone to plant the radium salt within his bed. You see, I wish to kill him, slowly and torturously, the same way he had planned to let me die there in the bad lands. Also, I wished the instrument to be the radium he had stolen from me.

"But when, in the papers, he was reported to be getting better, and had been moved from the bed where I put the radium, then I knew he had escaped me again. I feared a trap however, in case the radium had been found. So I had one of my men, a negro, the one who first called Sommers, telephone Sommers to look for the radium in Mallory's former room.

"This cleared the way for me. I stole the radium again, and brought it here. I rented this house be near my enemy, when I first returned to the country."

"And the gases you made use of?"

"I manufacture myself. There is a laboratory on the third floor. The smoke screens I laid for protection; the brominated xylene was to throw the household and guards into confusion, so that we approach unobserved.

"We carried off Mallory, and my strong negroes brought him here. I gloated over my enemy, for I intended to leave him to die with the radium he had stolen from me. But to make his torture worse, and make him recall the woman he had taken from me, I returned for his daughter. Mallory should look upon her pain while he died."

The horrible cruelty of the man's hatred was so blatant that it made even the calloused detectives shudder.

The girl Edith stared with wide eyes at the enemy of her father. She clung to her lover, the chemist who had saved her.

CHAPTER XV
The Mistake

MALLORY, who had listened to the story with closed eyes, looked up.

"James!" he whispered.

He wished to say something to Tholl, or Tollerman as he was now known. Moran, keeping the prisoner tightly in his grip, approached the Radium King.

"I—I tried to find you later," whispered Mallory. "I did not see you fall. I turned off, angry as you were. When you did not come back, I sent searchers for you. No idea where you had fallen. The dead horse was found, but no trace of you. I thought you had wandered off into the bad lands and died. I staked the claims for myself and Nora, who would have married me anyway, became mine."

For the first time, terror lit the prisoner's face. "You lie," he screamed. "You lie!"

Moran jerked him away from Mallory, for the prisoner seemed about to do the helpless man an injury.

"I don't believe it," said Tollerman. "It can't be so! He lies."

"It's the truth," said Edith Mallory indignantly. "He told me the story when I was able to comprehend it and I know it is true. My mother knew it was true. She knew the searchers had been sent for you. If you had returned, you could have had your share of the discovery."

Tollerman's face twisted in pain. "My God, what have I done!"

* * * *

A stretcher was brought to take Mallory back to his home. Edith Mallory was able to walk, leaning on her lover's arm.

Moran had the prisoner in custody. He had been searched, before, and all weapons taken from him.

"I want to smoke," said Tollerman, as they started from the house. "Will you do me the favor of placing one of my cigars in my mouth?"

"Sure," said Moran genially. Now he had his prisoner, he was not the one to hear malice.

The detective found an expensive cigar in the prisoner's vest pocket, and though it was crushed it looked as though it would draw. He stuck it in Tollerman's mouth, and the prisoner chewed upon it as Moran bent over to strike a match for him.

Other detectives stood close by him; there was no chance of escape. Prisoners were always allowed to smoke.

"Come along, then," said Moran, when the cigar was lighted.

Suddenly, Tollerman, handcuffed to a big detective, went limp. He crashed to the floor, pulling his captor with him. Moran fell on him fearing a trick.

But the prisoner, frustrated finally, but no longer a prisoner, lay quiet. Tollerman was dead. A faint odor of almonds pervaded the room.

Lawson had gone ahead with Edith. He heard Moran's cries, and went running back.

"Potassium cyanide," he said. "It was in the cigar, Moran. Take care of it, and give it to the city chemists for analysis."

The chemist returned to the girl. "What is it?" she asked.

"Tholl is dead," he said gravely. "He took poison."

She clung to his arm. "How horrible it has been," she said. "Young, it has been frightful, this strain. But the wonderful thing about it, darling, is that it brought you to me. If it had not happened, I wouldn't have you."

He kissed her tenderly. Together, they entered the grounds of the Mallory estate, happy in their love. The chemist had found a lodestone which turned life's baser metal to gold, gold more precious than the radium which had brought them together.

The End