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."