In the beginning there was nothing at all, and then things were created, and the wonder of created things was very great. When men became, they marveled at the richness and the beauty about them, and their lives were filled with astonishment at the myriads of things in the air and on the earth and in the sea. For many centuries they were busy taking note of all the created things that were. They forgot that there was such a condition as emptiness.

But there were six people in a certain solar system who really knew what emptiness amounted to. Five of them were in a fortress which was an asteroid and a mystery. One was in a small, crude object which floated steadily out from Earth. This one's name was Nikolai. The rest of it does not matter. He had been born in a small village in the Urals, and as a little boy he played games with mud and reeds and sticks and dogs and other little boys. As a growing youth he dutifully stuffed his head with things out of books, and some seemed to him rational and marvelous, and some did not make much sense but were believed by everybody. And who was he to go against the wise comrades who ran the government and protected the people from wars and famines and the schemes of villainous capitalists?

As a young man he was considered promising. If he had been interested in such matters, he might have had a moderately successful career in politics, as politics was practised in his nation. But he liked things. Real things.

When he was a student in the university he kept a canary in his lodgings. He loved it very much. There was a girl, too, about whom he dreamed splendidly. But there was a need for school teachers in Bessarabia, and she went there to teach. She wept when she left him. After that Nikolai studied with something of desperation, trying to forget her because he could not have her.

He thought of such past events as he drifted outward from Earth. He was the passenger, he was the crew of the manned space-probe his government had prepared to go out and investigate strange signals coming from emptiness. He was a volunteer, of course. It was a great honor to be accepted, and for a while he'd almost forgotten the girl who was teaching school in Bessarabia. But that was a long time ago, now. At first he'd liked to remember the take-off, when brisk, matter-of-fact men tucked him in his acceleration-chair and left him, and he lay staring upward in dead silence—save for the ticking of an insanely emotionless clock—until there was a roar to end all roars and a shock to crush anything made of flesh and bones, and then a terrible, horrible feeling of weight that kept on and on until he lost consciousness.

He could remember all this, if he chose. He had a distinct recollection of coming back to life, and of struggling to send off the signal which would say that he had survived the take-off. There were telemetering devices which reported what information was desired about the bands and belts of deadly radiation which surrounded the planet Earth. But Nikolai reported by voice, because that was evidence that he had passed through those murderous places unharmed. And his probe went on and on outward, away from the Earth and the sun.

He received messages from Earth. Tinny voices assured him that his launching had gone well. His nation was proud of him. Enormous rewards awaited him on his return. Meanwhile—The tinny voices instructed him in what he was to say for them to record and broadcast to all the world in his honor.

He said it, with the Earth a small crescent-shaped bit of brightness behind him. He drifted on. The crescent which was Earth grew smaller and smaller as days went by. He took due care of the instruments of his space-vehicle. He made sure that the air apparatus behaved properly. He disposed of wastes. From time to time he reported, by voice, information which automatic devices had long since given in greater detail and with superior accuracy.

And he thought more and more about the girl—teaching school in Bessarabia—and his canary, which had died. Days went by. He was informed that it was time for him to make contact with a drone fuel-rocket sent on before him. He watched the instruments which would point out where it was.

He found it, and with small auxiliary rockets he made careful tiny blastings which guided his vehicle to contact with it. The complex machinery for refueling took effect. Presently he cast off the emptied drone, aimed very, very carefully and blasted outward once more. The shock was worse than that on Earth, and he knew nothing for a long, long time. He was horribly weak when he regained consciousness. He mentioned it in his reports. There was no comment on the fact in the replies he received from Earth.

He continued to float away from the sun. It became impossible to pick out Earth among the stars. The sun was smaller than he remembered. There was nothing to be seen anywhere but stars and more stars and the dwindling disk of the sun that used to rise and set but now remained stationary, shrinking.

So Nikolai came to know emptiness. There were points of light which were stars. They were illimitable distances away. In between was emptiness. He had no sensation of movement. Save that as days went by the sun grew smaller, there was no change in anything. All was emptiness. If his vehicle floated like this for ten thousand times ten thousand years, the stars would appear no nearer. If he got out and ran upon nothingness to get back to where he could see Earth again, he would have to run for centuries, and generations would die and nations fall before he caught the least glimmer of that thin crescent which was his home.

If he shouted, no man would ever hear, because emptiness does not carry sound. If he died, there was no earth into which his body could be lowered. If he lived, there was nowhere he could stand upright and breathe clean air and feel solidity beneath his feet. He had a destination, to be sure, but he did not really believe that he would ever reach it, nor did he imagine he would ever return. Now he dismissed it from his thoughts.

He found that he was feverish, and he mentioned it when the tinny voices talked urgently to him. He guessed, without emotion, that he had not passed through the deadly radiation-belts around Earth unburned. He had been assured that he would pass through them so swiftly that they would be quite harmless. Now he knew that this was a mistake. His body obeyed him only sluggishly. He was dying of deep-seated radiation burns. But he felt nothing.

Voices waked him to insist that he make contact with another fuel-drone. He exhausted himself as he dutifully obeyed commands. He was clumsy. He was feeble. But he managed a second refueling. And even as he performed the highly technical operation with seemingly detached and reluctant hands, he thought of a schoolteacher in Bessarabia.

Before he fired the new fuel which would send him onward at what would be more than escape velocity, he almost humorously—yet quite humorlessly—reviewed his life. He considered that he might have no later opportunity to do so. There were three things he had done which no man had done before him. He had loved a certain small canary, and he remembered it distinctly. He had loved a certain girl, and in his weakened and dying state he could see her much more clearly than the grubby interior of the space-probe. And the third thing—

He had to cast about in his mind to remember what it was. His hand poised upon the rocket-firing key, he debated. Ah, yes! The third thing was that he had learned what emptiness was.

He pressed the firing-key. And the space-probe spouted flames and went on. Before the fuel was exhausted it had reached a velocity so great that it would go on forever through interstellar space. It would never fall back toward the sun, not even after thousands of years.

The knowledge of emptiness possessed by the five in the asteroid was different. A totally empty room is intimidating. A vacant house is depressing. The two-mile-long asteroid, honeycombed with tunnels and corridors and galleries and rooms, was like a deserted city. Those who had left it had carefully stripped it of personal possessions, but they'd left weapons behind, ready to be manned and used. They'd left a warning device to call them. The recall device was proof that the danger had not been destroyed and might return. And the plaintive call through all the solar system proved that it was returning.

There was irony in the fact that Earth had panicked when it seemed that intelligent non-human beings signaled from space, and that shrill disputes for advantage began instantly Burke reported no living monsters at the signals' source. The fortress and its call meant more than the mere existence of aliens. It was proof that there were entities of space who needed to be fought. It proved the existence of fighting ships of space; of deadly war in emptiness; of creatures who crossed the void between star systems to conquer and to murder and destroy.

And such creatures were coming.

Burke ground his teeth. Earth had fusion bombs and rockets which could carry them for pitifully short distances on the cosmic scale. This fortress was incomparably more powerful than all of Earth's armament put together. A fleet which dared to attack it must feel itself stronger still. What could Earth do against a fleet which dared attack this asteroid?

And what could he and Holmes and Keller do against such a fleet, even with the fortress, when they did not yet understand a single one of its weapons?

Burke worked himself to exhaustion, trying to unravel even the simplest principles of the fortress' armament. There were globes which were, obviously, the long-range weapons of the garrison. They were stored in a launching-tube at the far back of the compartment. But Keller could not unravel the method of their control. There was no written matter in the fortress. None. A totally unknown language and an unfamiliar alphabet would prevent written matter from being useful, ordinarily, but in technical descriptions there are bound to be diagrams. Burke felt desperately that in even the most meaningless of scripts there would be diagrams which could be puzzled out. But there was nothing. The builders of the fortress could have been illiterate, for all the signs of writing that they'd left.

Keller continued to labor valiantly. But there was no clue to the operation of anything but the transmitter. That was understandable because one knew where the message went in, and where it came out for broadcast. With the apparatus before one, one could deduce how it operated. But no one could guess how weapons were controlled when he hadn't the least idea of what they did.

On the third night in the asteroid—the third night by ship-time, since there was neither day nor night in the great empty corridors of the fortress—Burke dreamed his dream again. It was perfectly familiar, from the trees with their trailing leaves, to the markings on the larger moon. He felt the anguished anxiety he'd so often known before. He grasped the hand-weapon and knew that he was ready to fight anything imaginable for the person he feared for. He heard small fluting sounds behind him, and then he knew that someone ran breathlessly behind the swaying foliage just ahead. He felt such relief and exultation that his heart seemed about to burst. He gave a great shout and bounded to meet her—

He waked in the small ship in the entrance tunnel. All was silent. All was still. The lights in the control-compartment of the ship were turned to dim. There was no sound anywhere. The opened air-lock doors, both inner and outer, let in a fan-shaped streak of brightness which lay on the floor.

Burke lay quiet, still wrought up by the vivid emotions of the dream.

He heard a stirring in the compartment below, occupied by Sandy and Pam. Someone came very quietly up the ladder-like stairway. Burke blinked in the semi-darkness. He saw that it was Sandy. She crossed the compartment to the air-lock. Very quietly, she closed the outer door and then the inner. She fastened them.

Burke said, sitting up, "Why'd you do that, Sandy?"

She started violently, and turned.

"Pam can't sleep," she said in a low tone. "She says the fortress is creepy. She feels that there's something hiding in it, something deadly and frightening. When you leave the air-lock open, she's afraid. So I closed it."

"Holmes and Keller are out," said Burke. "Keller's trying to trace down power-leads from the instrument-room to whatever power-source warms and lights everything. We can't lock him out."

Sandy obediently opened the air-lock doors again. She turned toward the ladder leading downward.

"Sandy," said Burke unhappily, "I know I'm acting like a fool."

"You're doing all right," said Sandy. She paused at the top of the ladder. "Finding this—" she waved her hand about her—"ought to put your name in the history books. Of course you'll be much disliked by people who intended to invent space travel themselves. But you're doing all right."

"I'm not thinking of that," said Burke. "I'm thinking of you. I was going to ask you to marry me. I didn't. If we live through this, will you?"

Sandy regarded him carefully in the dim light of the ship's interior, most of which came through the air-lock doors.

"There are some conditions," she said evenly. "I won't play second fiddle to an imaginary somebody behind a veil of dreamed-of leaves. I don't want to make conditions, Joe. But I couldn't stand your feeling that maybe in marrying me you'd give up your chance of finding her—whatever or whoever she is."

"But I wouldn't feel that way!" protested Burke.

"I'd believe you did," said Sandy. "And it would amount to the same thing. I think I made a mistake in coming along in the ship, Joe. If I weren't along you might have missed me. You might even—" she grimaced—"you might even have dreamed about me. But here I am. And I can't compete with somebody in a dream. I won't even try. I—I can't imagine marrying anybody else, but if I do get married I want to be the only girl my guy dreams about!"

She turned again to the ladder. Then said abruptly, "You didn't ask why Pam feels creepy, or where. There's a place up on the second gallery where there's a door that's still locked. Pam gets the shivers when she goes by it. I don't. The whole place is creepy, to me."

She went down the ladder. Minutes later Holmes and Keller arrived.

Holmes said curtly, "The machinery in the transmitter-room reached a change-point just now. Those red dots in that plastic plate apparently started the transmitter in the first place. When its calls were answered it changed the broadcast, adding a directional signal. Just before we started out from Earth the red sparks passed another place and changed the broadcast again. Now they've passed a third place. We were there when the machinery shifted all around on a signal from that thing which hovers close to the red sparks and watches them. The transmitter probably blasted out at four or five times its original volume. There must have been a hundred thousand kilowatts in it, at least. It looks serious. Whatever those red sparks represent must be close."

Keller nodded in agreement, frowning, then he and Holmes wearily prepared to turn in. But Burke was upset. He knew he wouldn't be able to sleep.

"Pam gets the creeps when she passes a certain locked door up on the second gallery. I never noticed it, but I'm going to get that door open. We got to look into every compartment of this thing! There's bound to be something informative somewhere! Close the air-lock behind me so Pam can sleep."

He went out. Behind him, Holmes looked at Keller.

"Funny!" he said drily. "We're all scared. I feel uneasy all the time, without knowing why. But if he's as scared as I am, why doesn't he worry about going places alone?"

The same question occurred to Burke. The atmosphere of the brightly lighted halls was ominous and secretive. A man alone in a vast empty building would feel queer even in broad daylight with sunshine and other humans to be seen out of any window. But in this monstrous complex of tunnels and rooms carved out of solid stone, with uncountable millions of miles of pure emptiness without, the feeling of loneliness was incredible. He reflected wryly that a dog would be a comforting companion to have on such a journey as his.

He went down the long gallery with doors on either side. Past the room with the piled metal ingots. Past the door through which one saw hundreds of ten-foot metal globes. Up a ramp. Past the rooms where something like bunks must once have stood against the walls. A long way along this corridor. Emptiness, emptiness, emptiness. Innumerable echoings of his footsteps on the stone.

Three times he stopped at doors that had swung shut, but none was fully closed. All yielded readily. Then he came to the door Sandy had spoken about. He worked the handle repeatedly. It was firmly shut. He kicked the door and with a loud click it swung open.

There were lights inside this room, as everywhere else they had explored. But it was nearly impossible to see any distance. This was an extremely long room, and it contained racks of metal which reached from floor to ceiling. Each rack was a series of shallow metal troughs, and in each trough there was a row of crumbly black metal cubes, very systematically arranged. Each side was about three inches square, and they were dull black, not glistening at all. They filled the racks completely. There were narrow aisles between the rows of racks, through which Burke could make his way easily enough, but which a more portly man might have found inconvenient.

He stared at a trough, and was stunned. He picked up one of the cubes, and immediately recognized the object in his hand. It was a dull-black, smudgy cube exactly like the one his uncle had brought back from the Cro-Magnon cave in France. He knew that if he dropped this object—found two hundred seventy million miles from the other one—it would split into thousands of tissue-thin, shiny pieces.

He did drop it. Deliberately. And it shattered into layers which lay like films of mica on the floor.

For no clearly understandable reason, Burke found that his flesh crawled. He had to force himself to stay in this room with so many thousands of the enigmatic cubes. There had been a cube of this kind on Earth. The one he'd known as a child had belonged to a Cro-Magnon tribesman ten thousand, twenty thousand, how many years ago? And it could only have come from this asteroid. Which meant—

Presently he made his way back to the spaceship. He carried one of the cubes, rather gingerly. He meant to show it to Sandy. But the implications were startling.

Members of the garrison of this fortress, thousands of years gone by, had visited Earth. One of them, doubtless, had carried that other cube. Why? When the garrison abandoned the asteroid they left these cubes behind. They left behind intricate machinery to call them back. They left squat machines and ten-foot globes which must be weapons. They left nothing that would be useful in the place to which they had removed. But they'd left these cubes, hundreds of thousands of them.

The cube, then, could be anything. It could be impersonal, like equipment for the fortress that would be useless elsewhere. The fortress' equipment was designed to deal out death. Were the cubes? No. Burke had owned one without damage. When that cube split into glistening, tissue-thin plates, no one was injured. To be sure, there was his dream. But the cube wasn't a weapon. Whatever else it might be, it was not dangerous.

He went into the spaceship and for no reason whatever firmly locked both air-lock doors. Holmes and Keller were asleep. There was no sound from the lower compartment occupied by Sandy and Pam.

Burke put the black object on the control-desk. The single cube on Earth had been meaningless. The museum which joyfully accepted Cro-Magnon artifacts from his uncle had dismissed it as of no importance. It was fit only to be given to an eleven-year-old boy. But a roomful of such cubes couldn't be without meaning!

He dismissed this newest mystery with an almost violent effort of his will. It was a mystery. Yet there was no intention to have the fortress seem a mystery to whoever answered its call to space. He could guess that the signals were notification of some emergency which needed to be met. The automatic apparatus of the ship-lock was set to aid those who came in response to the call. But everything presupposed that those who came would know why they came.

Burke didn't. The thing must be simple, an explanation not yet thought of. But there was nowhere to start to think about it! His recurrent dream? No. That was as mysterious as the rest.

Burke was very, very lonely and depressed. He could look for no help in solving the mystery. Earth was now past the point of conjunction with M-387, and moved nearly a million miles a day along its orbit, with nearly half of them away from the fortress. At the most hopeful estimate, it would be three months or later before an emergency space fleet of replicas of his own ship could lift off from Earth for here.

And Burke was reasonably sure that the red sparks would have reached the center of the disk in much less time than that. If it were in some fashion like a radar, making a map of the surroundings of the asteroid, the observer's place would be in the middle. In that event, whatever the red sparks represented would reach the fortress before more ships came out from Earth.

He sat with his chin on his chest, wearily debating the impossibility of meeting a situation in which all humanity might well be involved. His achievement of space travel provided no sense of triumph, and the discovery of the abandoned fortress produced no elation. Not when a desperate emergency requiring a non-existent garrison to report for duty was so probable. Burke sat in the control-chair and could find no encouragement in any of his thoughts....

He heard a trumpet-call and was on his feet, buckling familiar equipment about him. There were other figures all around in this bunkroom, similarly equipping themselves. Some grumbled. There was a rush for the doorway and he found himself one of a line of trotting figures which swung sharply out the door and went swiftly down one of the high-ceilinged corridors. The faces he saw were hardbitten and resentful. They moved, but out of habit, not choice. There were other lines of men in motion. Some rushed in the same direction. Others ran stolidly into branching corridors and were lost to sight. Up a ramp, with the pounding of innumerable feet filling his ears with echoed sound. Suddenly there were fewer men before him. Some had darted through a doorway to the right. More vanished. He was at the head of his line. He turned into the doorway next beyond, and saw a squat and menacing object there. He swung up its side and seated himself. He dropped a helmet over his head and saw empty space with millions of unwinking stars beyond it. He waited. He was not Burke. He was someone else who happened to be the pointer, the aimer, of the weapon he sat astride. This might be a drill, but it could be action.

A voice spoke inside his helmet. The words were utterly strange, but he understood them. He tested the give of this lever and the response of that. He spoke crisply, militarily, in words that somehow meant this—a word missing—was ready for action at its highest rate of fire.

Again he waited, his eyes examining the emptiness he saw from within his helmet. A star winked. He snatched at a lever and centered it, snapping sharp, bitten-off words. The voice in his helmet said, "Flam!" He jerked the firing-lever and all space was blotted out for seconds by flaming light. Then the light faded and far, far away among the stars something burned horribly, spouting fire. It blew up.

Yet again he waited. He doggedly watched the stars, because the Enemy had some way to prevent detection by regular instruments, and only the barest flicker of one among myriad light-specks could reveal the presence of an Enemy craft.

A long time later the voice in his helmet spoke again, and he relaxed, and lifted the helmet. He nodded to the others of the crew of this weapon. Then a trumpet blew again, and he dismounted leisurely from the saddle of the ungainly thing he'd fired, and he and his companions waited while long lines of men filed stolidly past the doorway. They were on the way back to the bunk-rooms. They did not look well-fed. His turn came. His crew filed out into the corridor, now filled with men moving in a bored but disciplined fashion. He heard somebody say that it was an Enemy scout, trying some new device to get close to the fortress. Eight weapons had fired on it at the same instant, his among them. Whatever the new device was, the Enemy had found it didn't work. But he knew that it needn't have been a real Enemy, but just a drill. Nobody knew when supposed action was real. There was much suspicion that there was no real action. There was always the possibility of real action, though. Of course. The Enemy had been the Enemy for thousands of years. A century or ten or a hundred of quietude would not mean the Enemy had given up....

Then Burke found himself staring at the quietly glowing monitor-lights of his own ship's control-board. He was himself again. He remembered opening his eyes. He'd dozed, and he'd dreamed, and now he was awake. And he knew with absolute certainty that what he'd dreamed came from the black cube he'd brought back from the previously locked-up room. But there was a difference between this dream and the one he'd had for so many years. He could not name the difference, but he knew it. This was not an emotion-packed, illusory experience which would haunt him forever. This was an experience like the most vivid of books. It was something he would remember, but he would need to think about it if he were to remember it fully.

He sat stiffly still, going over and over this new memory, until he heard someone moving about in the compartment below.

"Sandy?"

"Yes," said Sandy downstairs. "What is it?"

"I opened the door that bothered Pam," said Burke. Suddenly the implications of what had just occurred began to hit him. This was the clue he'd needed. Now he knew—many things. "I found out what the fortress is for. I suspect I know what the signals were intended to do."

Silence for a moment. Then Sandy's voice. "I'm coming right up."

In minutes she ascended the stairs.

"What is it, Joe?"

He waved his hand, with some grimness, at the small black object on the control-desk.

"I found this and some thousands of others behind that creepy door. I suspect that it accounts for the absence of signs and symbols. It contains information. I got it. You get it by dozing near one of these things. I did. I dreamed."

Sandy looked at him anxiously.

"No," he told her. "No twin moons or waving foliage. I dreamed I was a member of the garrison. I went through a training drill. I know how to operate those big machines on the second level of the corridor, now. They're weapons. I know how to use them."

Sandy's uneasiness visibly increased.

"These black cubes are—lesson-givers. They're subliminal instructors. Pam is more sensitive to such stuff than the rest of us. It didn't affect me until I dozed. Then I found myself instructed by going through an experience in the form of a dream. These cubes contain records of experiences. You have those experiences. You dream them. You learn."

Then he said abruptly, "I understand my recurrent dream now, I think. When I was eleven years old I had a cube like this. Don't ask me how it got into a Cro-Magnon cave! But I had it. One day it dropped and split into a million leaves of shiny stuff. One got away under my bed, close up under my pillow. When I slept I dreamed about a place with two moons and strange trees and—all the rest."

Sandy said, groping, "Do you mean it was magnetized in some fashion, and when you slept you were affected by it so you dreamed something—predetermined?"

"Exactly," said Burke grimly. "The predetermined thing in this particular cube is the way to operate those machines Holmes said were weapons." Then he said more grimly, "I think we're going to have to accept the idea that this cube is an instruction device to teach the garrison without their having to learn to read or write or think. They'd have only to dream."

Sandy looked from him to the small black cube.

"Then we can find out—"

"I've found it out," said Burke. "I guessed before, but now I know. There is an Enemy this fortress was built to fight. There is a war that's lasted for thousands of years. The Enemy has spaceships and strange weapons and is absolutely implacable. It has to be found. And the signals from space were calls to the garrison of this fortress to come back and fight it. But there isn't any garrison any more. We answered instead. The Enemy comes from hundreds or thousands of light-years away, and he tries desperately to smash the defenses of this fortress and others, and when he succeeds there will be massacre and atrocity and death to celebrate his victory. He's on the way now. And when he comes—" Burke's voice grew harsh. "When he comes he won't stop with trying to smash this place. The people of Earth are the Enemy's enemies, too. Because the garrison was a garrison of men!"