Dan Lothar fell into the seal of Neptune and found himself in the midst of interstellar war.

CITADEL OF THOUGHT

by James Blish

(Author of "Bequest of the Angel," "Emergency Refueling," etc.)

CHAPTER I

WHEN Dan Lothar's shattered Ganymedian dropped into the ammoniac mists of Neptune, turning slowly and trailing a wraith-like, ephemeral fan of incandescent gaB, there was nothing to show the watching police cruiser that death was not waiting to enfold it below. The cruiser's job, after all, was done; the Ganymedian was crumpled, seared, riddled, and falling out of control to a bleak and uninhabited planet; the cruiser's young captain, who still required his men to call him "sir," was justly proud of himself.

That he did not take into account Lothar's phenomenal resourcefulness was perhaps wrong; yet he had beaten the interplanetary outlaw in a fair duel between ships, and more experienced men than the young commander had been satisfied with less. Withal he should have known that no police cruiser could have beaten the wasp-like Ganymedian unless there was something wrong inside; he should have remembered the shrewd mind behind Lothar's dark eyes, and the ability of that mind to take full advantage of chance. But the police cruiser went back toward the sun, and if a spaceship can strut, it did so.

For there had been much amiss within the Ganymedian when it blundered so carelessly into range of the cruiser's fire. Nothing was wrong with the ship itself—Lothar was too careful of it and too much in love with its sleek, deadly beauty, mothering it constantly with oily hands. No, it was the hand at the boards that was out of control. Dan Lothar was sick.

Any other man would have been dead. His lungs were burning unendingly with the corrosive purple mists of lo; his eyelids rasped over dry balls that saw everything as if at a great distance through a milky film. The bronzed skin was sallow, the cheeks sunken, the black hair singed; and from a razor-edged slash across the right shoulder unclotting blood oozed constantly. Every movement was a dull agony, pierced through as if by a white-hot sword from the shoulder-wound. His fingers refused to obey, moving in clammy independence at each impulse from the fighting brain; the dials on the board conveyed no meaning. Never-ending flight was Dan Lothar's chosen life, and again it had led him across deadly alien worlds before it gave him brief rest. Since he had left the Earth ten years ago, stifled by routine and toy sophistication. nearly every planet in the system had felt his flying feet and reached for him with a million deadly hands;, now it seemed that Jupiter's poisonous moon would claim him as a proxy conquest.

He managed to get into his spacesuit and fight the Ganymedian, driving the quivering, wasted body as if it did not belong to him. That was his way, the terrible drive of his brain which would never let him rest; but even against the will of Dan Lothar, who had thrown himself deliberately against five worlds out of sheer disgust, nature took its wonted toll....

And so it was that the tiny planet-plane. mangled beyond recognition, plunged into the dry, cold atmosphere of Neptune, and a slumped spacesuited figure sat strapped in its metal seat, head rolling grotesquely... and before it a jury-rigged rocket tube, such as the spacelanes had not seen since geotrons were invented in 1987, coughed, popped, hissed....

CHAPTER II

STRANGE disconnected images swept through his brain as he forced himself to consciousness. At first they were long-forgotten scenes on Earth— dinner-suits and tall candies—a humming cyclotron—a bright, silent peal of laughter from a brown-framed face. The face moved nostalgically above brighter waving fields of grain; the waves persisted, now green and white-ridged water, while the face faded. For long ages he saw nothing but rolling water, moaning and sighing through his head.

Then at last the sea-waves merged into a single harsh green glow; the glow centered in a single tube-light directly above his head. He winced and closed his eyes; red spots floated persistently before them in protest. He remembered his battered body and gritted his teeth in anticipation as he turned his head away from the glare; but there was no answering stab of pain. Tentatively he moved his arm; it came up to his shoulder freely, in complete control, without any abnormal sensation. His wasted muscles no longer ached; the fire had been drawn out of his lungs. He took an appreciative breath, noticing the faint musty odor with relish, and opened his eyes again. Once more he had cheated the ebony gates, borrowed another short period of life.

The room in which he lay convinced him that it was not a very long respite. It was unfurnished, prison-bare stone, bleak in the light of mercury-vapor. The Plutonian mines! It was too cold to be Venus; the light was not calculated for human eyes. Photocells were more sensitive in such illumination, and the mine guards were robots, for no free man would take such a job. Probably the cruiser had followed him down, vulture-like, and finding him still alive, had remembered the larger reward for the living criminal, brought him here. He did not then consider his healed wounds, for circumstantial confirmation was placed upon his befuddled theorizing.

A silver egg drifted into his field of vision, watched him through two black eye-lenses. A proxy-robot. A new model, apparently, far advanced over those he had beaten in his escape from the radium mines years ago. It had no appendages for weapons, but there was another opening, slot-like, below the eyes which might be a porthole for a ray. It gave the front end of the egg a severe schoolmarm expression; he chuckled grimly.

"You are well," said the proxy abruptly. "You can stand." It was not a question, but a cross between a statement of fact and a command. The metallic voice startled him; without thinking he climbed to his feet, flexing his muscles. He was indeed in perfect condition, better than before he had started the wild race across Io. The fact, startling enough in itself when he considered the cold stone upon which he had made this recovery, was subordinated by the sight of an open door behind the proxy. Not even a door, but a bar-less doorway. He had not seen it before; it seemed as if it had just sprung into being. He considered a break, but the proxy was too high to grab and watching carefully.

"This is Pluto, I suppose," he said. "The bad penny has returned to the mint."

"Follow," the adding-machine voice replied, and the egg pointed its prim face out the doorway, swooped forward. He strode after it, but some instinct made him turn as he entered the corridor. There was no door behind him—only a solid wall!

"Tricky," he murmured, and grinned. Tricky prisons were easiest to break.

But he became increasingly bewildered as he followed the proxy down the green-lit corridor. He passed several doorways to his right and left, and what he saw beyond them was not prison-like. It was more like the interior of a stone spaceship, crowded with machinery, some of it familiar, most of it incomprehensible and technically senseless. A bad boy turned loose in a fortress with a toy construction set and a box of old radio parts might have produced most of what he saw; yet it all spun, whirred, and blinked purposefully. Nowhere did he see an attendant, although a few of the proxies were poised motionlessly here and there as if watching.

Another blank wall came into view around a bend; he waited for it to vanish from his path. Instead the proxy shot up and disappeared, leaving him standing at the bottom of a tremendous shaft, into which light radiated at intervals as far as he could see. The egg had vanished, but finally appeared, floating in a beam of green far above his head, apparently waiting for him to follow.

"I'm no damn' bird," he protested, and immediately shot upward, arms and legs asprawl. In a moment the unexpected force had brought him up beside the egg and deposited him, breathless, on another stone floor. He stood motionless, gaping.

CHAPTER III

THIS was certainly not Pluto; beyond that negative he could say nothing of what he saw. Before him was a huge hall, about two stories high, and seemingly as long as the levitation shaft was high. Its sole furnishings were a number of tilted couches dotting the floor, in each of -which lay a sleeping figure. The light was, as ever, bright blue-green and hard on the eyes; yet apparently this was a vast dormitory for all the human occupants of the weird place. The silence was absolute, empty of the machine-mutters with which he had lived in his lost Ganymedian; it seemed to wash in his ears with seashell sounds. He recognized the effect as the cause of his dreams before awakening.

"The egg must have slipped," he thought in awe. "This is the boudoir."

Then horror struck him as he saw that every eye in his range of vision was open, staring glassily ahead. His flesh crawled; he grasped his raytube automatically, not surprised to find it there. Under the green radiance they all seemed ghastly corpses, yet breathing movements were clearly evident.

"Thinking," he told himself unsteadily. "Contemplating their psychic navels, that's what." He shivered in the unnatural silence.

"Daniel Lothar." a voice whispered in his ear. He swung, but all the eyes were regarding him, and he could not tell who had spoken. His nerves were quivering.

"It is I," said the voice. "Here." He felt his gaze being compelled to his right.

At first it appeared to be but another of the monstrous dreamers upon a slightly more ornate couch. Then he saw that it was a woman....

She might have been a beautiful woman, but her face was sallow in the unflattering light, her hair was swept back from her forehead so that her brain-case seemed to bulge. Yet the bulge was merely optical, for she seemed perfectly formed.... Her eyes claimed his; he felt himself drawn down, down, into deeper wells than he had ever known. All the loveliness of this woman, who seemed physically little more than a girl, was annulled by those eyes, which burned with a cold, subtle fire, detached, ascetic, powerful. He could not fight those eyes, though his will had met five worlds. Or perhaps he would not, subconsciously....

"You are the first outsider to come since the Hall was built," the whispering voice went on. "We bid you welcome."

"Where am I?" he tried to say, but his lips would not form the words.

"You are in the Hall of Thought, on Neptune, at the bottom of the Sea."

The Sea, Dan Lothar remembered, was liquid gases, mainly methane.

"How did I get here, then?"

"You fell in your ship; we brought you in." She fell silent, contemplating him with those unspeakably inhuman eyes; it came to him that she had not moved her lips either during the entire conversation. Mind to mind—something puzzled him.

"I was injured," he began.

He felt a sensation of cold amusement, not laughter, but faint contempt. He wondered if she had forgotten what real laughter was, lying here thinking to herself.

"Do you suppose your bodily ailments have any moment in the Hall of Thought? The mind controls the body, as it controls, perhaps creates, all matter. Tell me... how old do you think I am, then?"

"If you'll stop looking at me..." He sensed faint apology and the mental compulsion was withdrawn. With the icy mental flame gone he could see her more clearly. Accounting for the green light, she was not at all bad. Better than he at first thought.

"About twenty," he judged, speaking the words now.

"The figure," said the incomprehensible girl, "is closer to two hundred and twenty."

CHAPTER IV

SHE MOVED an arm slightly; approached and sat down at her sign at the foot of the couch, perching tensely on the edge. Wryly he remembered another time he had done the same thing but not in a room with hundreds of other beds, at the bottom of a sea of liquid gases! He tried to concentrate on the two hundred and twenty. It sounded impossible. And yet so much in the Hall of Thought was just that—the strange machinery, the vanishing doors, the serried silent philosophers, his own quick recovery—figments of an Etaoin pleasure-palace dream.

"When I was a little girl on Earth, about 1965, I was adopted by a college of metaphysicians." Again the sensation of amusement. "They were blunderers compared to our present advancement, but they accomplished one thing. They taught me to believe death was unnecessary." She paused. "I was never allowed to think anything about dying. I was told, and had no reason to think otherwise, that no one had to die, that I never would. My mental powers, groomed by them to greater ability, directed on that one lesson, pounded into me ceaselessly... well, I am deathless."

He shut his mouth with a click. Crazy! This was the most fantastic feature yet. But the powers of mind over matter were known.... A fragment of an old creed came back to him: "There is no life, truth, intelligence, nor substance in matter. All is mind, and its manifestation...." That was misquoted, but the idea was there.

He shuddered again. So that was the reason for this silent hall! Immortals, sitting or lying in eternal thought... a defiance of nature?

She divined his thought. "The Hall has another function than contemplation, Dan Lothar. Were we dedicated to that alone, you would not have been brought here. Perhaps some day we may devote ourselves to the pursuit of the cosmic comprehension, but now there is another task set us."

He made no comment and she went on.

"Long ago we tried to reach that cosmic awareness. The massed minds of the college were flung out, united, in a great effort at understanding—but without warning came a terrible interruption. There was another thought present. At first it was a faint disturbance, nothing more, jarring our concentration. We could not find the source. Then, gradually as we became attuned to it, it grew; an alien thing, not human, and inimical, cold, deadly, coming from we knew not what nadir beyond our Earth.... How inhuman our Hall must seem to you, I realize," she interrupted, and he was astonished to see a faint smile transfigure the acerb expression for a moment, "but you have no idea of the difference between thought patterns of human and alien minds, no matter how advanced the former may be, until you have actually sensed them. We did. We felt this deadly current, this other-world pattern, playing coldly across the Earth, and we were afraid. We had no way of knowing its meaning, vet we did know that it meant ill things for man and his works. Soon after we began to piece it out... it was lost in the human thoughts all around us.

"We came out here, away from human interference, to search out that spatial cold we had felt. Only a few of us are immortal; but we are all doing the same work—tracing, projecting, attuning our mind-channels to that thought. You cannot imagine why it seemed so important, because you cannot feel what we did—yet it means death to mankind unless it is halted, Dan Lothar."

He put a hand to his head. Unbelievable nightmare! A citadel on acerb Neptune, built at unguessable cost, to seek a thought, a single wave, that seemed dangerous to Earth! The idea chilled him; yet on the surface it seemed ridiculous.

"I know," she said. "Close your eyes and I will show you."

CHAPTER V

AND immediately lie was sorry. He felt bis mind being probed by delicate, intangible fingers, opened, readjusted, sensitized, as if it was being made to think on another plane... and pouring in on him in stifling waves came...

There was no name for it in human speech. It was not words, nor pictures, nor physical sensation. It originated in no human mind, nor in any known mind of the Solar System. It was like the breath of Death, utterly horrible, utterly irresistible. It filled all space, charged it with unspeakable things; it was Fear, and Hatred, and emotions human beings had never known. It seemed directed at him personally, an implacable lust for his shrinking soul; yet it surged and swirled like a charnel wind over the universe of man so that all the great cities on the planets were darkened and human figures lost their life and became tiny wooden puppets immersed in cold, invisible flame. It blighted all hope and re-opened the ebony gates. It ran through his brain in rivulets of ice—

Then it all folded shut around him, like the turning of a page, left him white and trembling.

"You see?" the girl asked softly. He clenched his hands to stop the quivering. It was gone now, yet he knew he would never forget it; that in some measure, as long as the unthinkable mind that was broadcasting it lived, he would be able to sense it.

"What—what—is it?" he gasped.

"It is the approach of another world, another people," she said, her face like the expressionless marble of some ancient statue, lovely and lifeless. "They come from a far star, we do not know what one, and they are very near now."

"Why did you call me here?" He felt a faint anger. To die fighting in the outlawed paths of a flamboyant, understandable universe was as nothing to having lived and seen the gulfs of unsuspected things yawn below.

"For knowledge." She frowned slightly. "Our work here is done. Once we thought that we could project suggestions to them, influence their minds, but the patterns are too different. It is fighting that must be done now, star against star, before they can reach our system and carry out whatever purpose may be back of those deadly waves. And we cannot build a ship! None of us are technicians. The work on the Hall was done under the direction of a man now dead; we need you now for that knowledge."

He digested that. "Why didn't you warn the world, instead of sprawling here thinking at—Them?"

"The world has no weapons against such forces."

"But you must have—"

"The weapons are important, yet remember—we are meeting minds as well; minds skilled in all the powers of thought. We are the only ones equipped to fight a mental battle. With an ally for the physical fighting we may win. You must be that ally. We can protect your mind, but to call an Earth fleet would be throwing lives away—we could not possibly shield them all."

She arose, and as if it were a signal, the lights flashed yellow. It was a grateful change, and made the vast stone cavern seem almost cosy. A stir of motion ran over the Hall. Even the emotionless face of the immortal girl seemed more real. The men on the couches were arising and moving toward them.

"Tell me," she said. "Will you fight for Earth now, instead of against it?"

This was, at last, something that Dan Lothar understood. This talk of immortality, the powers of the mind, the dreadful power which had held him for a moment, had built but a hazy picture in his mind. But how clearly he could see himself riding a mighty cruiser, fighting some invader, burning space with lancing rays, riding the red clouds of dinitron recklessly as of yore! He smiled a little. It wouldn't be bad, and... he glanced sidewise at the girl. She was still lovely, no matter how many centuries she had lived, or how far back her hair was combed; she still had something to learn, with all her centuries, that no one in the Hall had thought to teach her but himself....

His smile broadened, and he nodded.

CHAPTER VI

HE WAS glad when the ship was finished. A wonderful ship, fast and powerful as none on Earth had ever been; but the way it had built itself under the lashing thoughts of the Hall as he ran the plans carefully through his mind was nerve-wracking and weird. The whole process took less than a week, during which no one ate, or seemed to require food, and no one slept but himself. Strange devices were attached to the generators. fitted awkwardly into the standard rayports he had supplied. He insisted also on a standard rocket rifle being installed in one turret. The girl was constantly at his side, her emotionless voice topping the crashing of the ship as it seemed to fling itself together: he noticed that she had undone the bun at the back of her head and arranged her hair more naturally. He grinned to himself. She was learning without knowing it. She looked almost attractive now, he admitted, even though the jarring mercury-vapor lights had been restored for the use of the proxies, which had appeared from nowhere in swarms.

At last the job was done. The intellectuals, like a group of eager children, wanted to get under way at once, but Lothar insisted on a week of training in the handling of the mechanisms and in astronautics. "Damned if I'll blast off with a crew of walking brains who don't know a C-tube from a ray-tube," he said. Finally he considered the requirements met, named the ship the Ganymedian II ("Bad luck to fly a nameless ship," he said, against the scoffings of the metaphysicians), and, surrounded by meteor screens drawn in close to prevent the "waters" of the Sea from crystallizing the metal skin, the great flier burst from the airlocks and mounted space over Neptune.

He locked the controls, sending the ship outward in a great arc which would bring it eventually to rest far beyond the boundaries of the Solar System, and turned to the girl.

"There's nothing to do now but sit," he told her. "You can put your organic robots back to bed."

She smiled for the second time since he had seen her. "I'm sorry that we all seem so inhuman to you," she said. "We've all been trained so thoroughly in abstractions that, well... we lose our hold on the things that are real to most people." She looked down at the loose mud-colored gown that she had worn since the first day. "I don't look much like a woman, do I?"

At that moment Don Lothar could not imagine her two hundred years older than he. He grinned broadly.

"There seems to be a stock of space-harnesses in the stores, since I thought of them in conjunction with the food and the other unnecessary items when we were building. Why don't you climb into one of those?"

The harness needed a few discreet adaptations involving small spare metal reflectors and several feet of leather to fit it for feminine use, but eventually she got it on. She looked even more human now. The shorts were very enhancing to unsuspected beauty.

"Now," she said. "Teach me something about the ship. I don't want to be so much useless brains."

They sat together at the board, and Lothar began the job of showing her the complexities of astronautics. It was a very pleasant few minutes, but only a few', because he never had to repeat anything or even explain complicated facts. She absorbed them instantly.

And just when Dan was feeling more natural the ominous nightmare reasserted itself. One of the younger metaphysicians popped into view from thin air, his white face strained.

"They are near," he said. "Nearer than we thought. We can feel them. And Di Falco and Guyer cannot handle the machine in chamber two."

DAN muttered to himself and punched buttons. "Damn' intellectuals." he commented, with additions. "What's the matter down there?"

"Something is wrong," the speaker rasped tinnily. "Come and see. We cannot control the current."

"I don't have to come and see," Dan roared. "What do you think I've got meters for? Cut the potver on the condensers before you burn us all to a cinder. Watch your input. Wake up. Think about something useful." The girl was actually grinning like a gamin when he turned away; he felt happy himself, although the specter of dread hung over him as it did over the whole ship.

"Now' you," he said to the startled young man. "Where are they?"

"Near," replied the other, waving his hands helplessly.

"Great Leonids! Where?"

"Wait a minute," the girl broke in. "They are 20 degrees off starboard, down ten degrees, and about a million miles away." Her face was expressionless again, but her tone seemed to be saying, "How am I doing?"

He turned to the boards and watched the detectors, flinging them out in a spherical screen to their farthest range. It seemed that his brief experience had sensitized him, for he could feel the cold alien breath faintly now. The indicators gave no sign.

And then, suddenly, the needles bobbed; simultaneously the Ganymedian II gave a terrible lurch which threw them all to the floor. The First Interstellar War was begun!

CHAPTER VII

THEY struggled to their feet, faces white. Dan climbed back into his seat and watched the detectors, the girl peering over his shoulder.

"What is it?" she cried.

"Tractor. Tripped automatically by the detector field. Nothing new." But he felt a, chill as he fingered the buttons. This sudden blow out of trackless and seemingly empty space! What horrors did it herald?

He bawled orders into the microphone; the ship, answering clumsily to the unskilful hands of the drivers, bounded free of the beam, arced in an unpredictable hyperbola toward the unseen enemy. The girl crouched breathlessly in the copilot seat; the young metaphysician climbed into the spacesuit locker and hid.

"Big help," grunted Lothar. His eyes remained glued to the screen, watching for the first sign of the approaching invaders. He had shut down the detectors for fear of setting off another relay. The floors quivered to straining generators.

"Balance that flow!" he ordered into the microphones. "Number Two, you're still using too much power. You're shaking the whole ship."

A tiny bright dot—too bright, it seemed, for reflected starlight—appeared on the screen, grew with agonizing slowness.

"Port turret," he snapped tersely. "Range four hundred thousand. Three hundred. Two hundred. Fire!"

Nothing happened. There was no flash of rocket rifle, no streak of ray. But a tenuous, almost invisible network of green light burst like fireworks far to one side of the white point and died away. Not bad shooting for this distance.

But from the white point on the visor screen, now fast becoming a disc, another point detached itself, floated deliberately toward them, seemed to pause a breathless instant, then arrowed for the stern as if magnetized. There was a flare and a racing tide of flame engulfed the whole tail of the Ganymedian II, growing like a fiery amoeba. Dials quivered; the song of the generators rose to a tortured howl.

"Cut the drivers!" he cried. The howling died out mournfully, but the sheath of flame still advanced, silently, swiftly, like a sentient cocoon. On a hunch Dan turned off the screens.

Immediately the white fire quivered, paused indecisively, and then streamed indifferently off into space and faded. Sweat broke out on his body. He jerked the ship forward again; again the pale green network flowered briefly beside the alien. It was fully visible now. not more than a thousand miles away, a windowless ball of metal, seeming to shine by its own radiance. The green network was flung across it, and Dan held his breath.

But beyond a slight temporary dimming of the white glow, the invader was unharmed when the green light faded.

"Stymied," Dan whispered.

As if hearing and understanding, the sphere broke its headlong drive toward them and looped over them toward the distant sun.

"After them," the girl panted. "Quick!"

And now began the grim chase....

CHAPTER VIII

WITHOUT hope, Dan tried one more shot from the regulation gun. As he expected, it rebounded harmlessly in a red dinitron flower before touching the fleeing sphere. It would have done so from an Earth vessel. After that no further shots were exchanged. The two, alien and Earthman, matched astronautics in silence, the one bent with deadly ferocity upon reaching some inhabited planet, the other doggedly clinging, hoping, waiting for an opening. Weird battle! The white sphere dodging, putting on speed, trying to lose its tiny bulk in the vastness of space, yet- unable to hide; the cruiser from the Hall of Thought pursuing always, while mentalities meeting action for the first time in their cloistered lives fastened grimly upon the betraying thought-waves, holding that fearsome spoor for the merely human pilot at the controls. Faster, faster, while the motionless stars mocked the climbing speed indicators.... Pluto's orbit was passed....

Abruptly the white sphere vanished from the screen, vanished utterly. In vain Dan Lothar searched the space ahead. The girl sat beside him, eyes burning coldly, white brow furrowed, and he felt once more the awe and sense of smallness at her aspect. She broke her strained silence as he scanned the meters frantically.

"They've stopped."

"What!"

"Yes... they're turning back."

"It isn't possible. They'd be crushed."

"Nevertheless, they did."

Dan braked the Ganymedian II until it seemed the acceleration would squeeze his bones to jelly despite the compensators. The girl gasped for breath, then was silent again, her face strained with concentration. He swung the ship laboriously around, while precious seconds flew by, and wondered what manner of things the silver sphere contained, to stop dead at full speed.

"There they—are—they did stop— how on earth—"

But there was no time for wondering, for the white sphere was plunging back toward Pluto. It was going to land!

Dan dropped after it and braked furiously, sweeping around the planet in a deceleration arc. The enemy ship flashed below them for an instant; the intellectuals on the gun deck fired four times at close range. All four shots were hits but they were out of sight before the effect could be determined.

"Nice," Dan breathed in surprise. "I wonder..."

"No," said the girl. "I can still feel them."

THE cruiser struck the frozen ground, bounced, and Dan let it ride free a moment. At last he grounded it in rough haste, and the keelplates screamed in protest through the very beams of the ship.

"We're only a few miles from them," the girl whispered. "You circled almost the whole planet."

"Yes," said Dan Lothar grimly, "and we're plunk in the middle of the Plutonian penal colony."

Indeed, the single dome which covered the main mine shaft, and the small field for receiving the infrequent freighters were visible through the ports. The few human guards who occupied the dome were runningout toward them in spacesuits. There were, Dan estimated hastily, about twenty of them. "Glad of the diversion, I'll bet," he thought. He switched on the radiophone.

"Commander!"

"Commander Cameron speaking. Who are you—that other ship—"

"Interstellar invaders. Dangerous, inimical, down about ten miles from here."

"What! Who are you, I say—"

"No time. Don't argue. It's life and death for you and the Earth as well. Break out your prisoner's and arm them. They're ray-screened, but I think they're vulnerable to gunfire now that their meteor screens are down. Quick!"

"We can't arm them all—and besides—"

"Never mind, arm as many as you can and get them into suits. No time for legal worries. This is interstellar war, you fool."

He cut the connection and opened the suit-locker, jerking the terrified young intellectual out of it. "Everyone into suits—no, not you—"

"I'm going," said the immortal woman, and he was too much in awe of her now to protest further.

As the airlock shut behind them the prisoners were bounding out of the dome in their suits. "Most of them trusties," said the commander. "The others have no love for Earth."

"I can imagine," Dan thought sardonically to himself, remembering the radium-eaten inmates.

Then, "Let's go!"

CHAPTER IX

AGAINST the light gravity of Pluto the trip was short. Behind them some of the guards dragged a few hastily dismounted rifles, and others clutched futile-looking rocket guns. The intellectuals carried long ray-tubes without grips, clumsy affairs obviously designed by amateurs but containing unknown powers. In a moment the white light of the invader glowed over the jagged, rocky horizon, and Dan again sensed faintly the terrible emanations.

"All right," he whispered, as if afraid the unguessable intelligences within that malign craft could hear. "Scatter. Their detectors must have us spotted but we're too small to hit Individually." The order had barely been a minute in execution when one of the fireballs floated silently over the hills and sent a creeping poo! groping toward them. There were no attracting screens around their suits, however; the shots had been blind, had caught no one. Quickly, taking advantage of every cover, the little party crept forward. The white sphere came slowly into full view, and into Dan's brain the evil thought-waves beat overpoweringly.

"Let 'em have it," he hissed softly, and raised ins own gun, trying to shield his eyes against the white light, which seemed at this distance to be penetrating his whole body. The dread current of fear rocked his mind, made him dizzy and sick, and he could not pull the trigger... the stars spun before him.

"Dan!" the girl's voice cut across the whirling universe, and it was as if a veil had lifted. Her own will had seized upon his, held it against the deadly force.

But not so with the others. Guns hanging limp, the prisoners and guards were straggling forward, rapt, powerless, toward the gleaming, radiant ship. And as they advanced, little balls of white fire, like monstrous eggs, rolled to meet them....

Around him the intellectuals crouched, their trained minds fighting the hypnotic effulgency, holding out mentally, yet with no power left over for physical movement. He tried to help the girl with his own will, the power with which he fought five worlds and death itself in his little Ganymedian, and suddenly found himself unshackled. He leapt to one of the discarded rifles, righted it, crowded a clip of five shells into it in terrible haste, pulled the cord blindly.

The shot was soundless, but the ground jolted under him and a red flash of dinitron marked the alien's hull. Around it the white light dimmed and began to disappear! He roared an insane laugh, pulled the cord again and again, continued pulling it in a scarlet haze long after the clip was exhausted. There was a huge dark patch on the glowing sphere— but the shots had not penetrated!

Not penetrated... but the intellectuals, their mighty minds pitted successfully against the now-dimmed light, raised their awkward tubes, concentrated on that crater; the green network flowered, grew, and ate mordantly where the screening radiation was gone.

ABRUPTLY it was all over. There was a silent burst of energy, green and white intermingled; the alien ship shattered like a glass bubble. Within they caught brief, horror-sickened glimpses of things forever unknowable and indescribable; then, that too, was gone; there was but a heap of scrap metal, dull and lifeless.

The girl sat back on a rock, slumped; for a moment it seemed she would faint under the release of the ghastly strain. But she was still the immortal mistress of the Hall of Thought, and after a moment she straightened with an effort, looked squarely at him.

"Now you see the power of the mind," she whispered. "Are you sorry I am so much an intellectual, Dan Lothar?"

It was an utterly human question.

"You still have something to learn," he replied. "There are other powers." He leaned toward her. The glass of their face-plates clinked, and then they both laughed—an explosive, free, and human sound beneath the black Plutonian heavens.