The Head Hunters

by William Morrison and Frederik Pohl

When such a superlatively gifted storyteller as William Morrison—remember his HOLLYWOOD HABIT, and DATE OF PUBLICATION, 2083 A. D.?—joins quills with Frederik Pohl of Ballantine pocket book fame an entertainment special is virtually assured. Here’s a documentary-type saga of interplanetary engineering and space hazards incalculable that starts brilliantly, gathers momentum with every breathtaking development on the frontiers of tomorrow, and ends with a smash climax that will set you to pondering for a long, long time.

The best “man” for a really tough engineering job in space may be a headless robot. But human courage rates a few shining medals too!

It was dull work, changing circuits in a vacuum, where every current-carrying atom had to be insulated against the spark-over of space. John Tinker stood up, yawned, and glanced through the tangle of equipment at the robots walking about outside.

He said into his helmet radio: “Chop, chop, chop.”

He couldn’t see the girl’s face, but her voice was disconcerted. “Chop—what are you talking about?”

“Them.” He waved at the robots. “Carrying their heads like old Anne Boleyn.” He sang: “With ’er ’ead tooked underneath ’er arm, she walks the bleddy Tower—”

The girl said: “They aren’t heads. They’re apex-mounted sense receptors. They aren’t arms. They’re powered torsional manipulators. They aren’t ‘tucked.’ The heads are plug-in. I mean—the receptors are plug-in, bayonet-mounted, and they fit at the apex while in use or in a dummy female base under the manipulator for carrying.”

Tinker said simply, “S. Cottrell, I love you.”

He thought he heard a snort over the radio, and he sighed. All the same, it gave him a queer feeling to see the headless creatures with the steel skulls clasped casually under their arms.

He had tried to tell his partner, Drake, about it once; but Drake was not a sensitive man. He had pointed out very quickly that there was nothing feminine or fragile about the robots, and had elaborated on the remark with a long obscene outburst about the lack of females on the asteroids.

Tinker, listening, had marveled; some of the words he had never heard before. No doubt a man had to go through Drake’s special training—in six jails—to learn them.

The girl said resentfully, “Are you going to help me or not?”

“It’s time to take a break,” Tinker objected. “Let’s watch the robots.” He waved at them as he spoke.

She hesitated, but she stood up and joined him. He wished he could see her face through the helmet of the space suit. She said: “I’d think you’d be used to them by now.”

“I don’t spend much time here,” he reminded her. “As you know, Drake and I have our quarters on Asteroid B, and we only come over here for trouble-shooting or checkups—half an hour or an hour at a time. It isn’t safe to stay long.”

“You’ve been here five hours already.”

“I won’t be here for six, though. Not if Drake will get off his back and show up.” He added: “Anyway, this is a special occasion. It’s worth taking on a little extra radioactivity to be with somebody like you.”

“Sure, somebody female,” the girl agreed. “Anybody female.”

He shrugged. It was true, in a way. It had been three months since he had seen a woman, any woman—or any man or child, for that matter, except himself and his partner. And Drake didn’t count. Tinker, striving to be just, had to face the fact that Drake wasn’t a man. He was a rat, with the fierce and treacherous disposition of a rat. In effect, Tinker lived alone and he didn’t like it.

But on the other hand, he liked this girl, even though he had never seen her face. Her voice alone made her seem maddeningly desirable—it was so warm and friendly.

He stared at her, trying to see through the faceplate, and quickly realizing that it was flatly impossible, unless he focused his headlamp directly in her eyes. There was no refracted light to illuminate the inside of her helmet, since refraction cannot take place in the absence of air. He could only determine with certainty, under the helmet and the protective armor, that she did have a face—and that she could stand on her own two legs. Whether the face was pretty, whether the legs would get a second look from him on Earth, he couldn’t tell—and it was posing a threat to his sanity.

She said, half-laughing, “I thought you were watching the robots.”

“I’d rather watch you.” Her laughter became wholly unconstrained. “You’re space happy,” she warned. “I could easily be three times your age. You don’t even know what I look like.”

“You sound incredibly young,” he told her. “Anyway, you aren’t too old to be charming. They don’t send hundred-year-old women to the asteroids.”

“No,” she admitted. “But the retirement age is sixty.”

“You aren’t sixty either,” he said positively. “You might even be under thirty.”

There really was some danger on Asteroid A. The automatic isotope plants, robot-run and remotely located in space, were a vital cog in the wheel of isotope manufacture. If anything went wrong on A, it could explode and destroy everything on its surface. But even if it took its nearest planetary neighbor—Asteroid Y-335 B—with it, the only lives at stake would be Tinker’s and his partner’s. And his partner, he was convinced, would be no great loss.

Of course, an explosion was unlikely. But there had been a disastrous blowup on Venus which had caused the Main Office hastily to set about locating new plantsites in the asteroid belt. So it was possible, theoretically—and even without a blowup, there was constant radiation seepage on A.

The healthiest man was better off if he stayed a maximum of six hours at a stretch—twenty-four would certainly have been fatal—and sick and decrepit individuals weren’t supposed to be there at all. Sixty? No, Tinker told himself, she couldn’t be a day over thirty. Well, forty, maybe....

“What’s your first name?” he demanded suddenly.

“My what?”

“Your first name. You said it was S. Cottrell. What does the ‘S.’ stand for?”

She said dubiously, “Siria. My father was—”

“I know,” he said exultantly. “You’re twenty-five! Your father named you in honor of the Sirius Expedition—you and possibly ten thousand other unfortunates. So it follows, as a mathematical corollary, that you can’t be a day over twenty-five.”

She said stiffly, “I happen to be twenty-three.”

“Even better,” said Tinker. “Siria, will you marry me?”

“No. Now, do we get back to work? Or do I get back to work and you go home?”

Tinker wasn’t a fool, for all that he liked to play games. The two of them went back to work. Around them, as they labored at the difficult task of rearranging the circuits in accordance with Siria Cottrell’s wiring diagrams, fresh from the Home Office, the robots moved mechanically about their affairs. They were making isotopes, and it was no concern of their electronic brains if human visitors decided to change the way in which they made them.

In vast, open-walled buildings on the far side of the asteroid, atomic nuclei were reacting. The process was slow, by atomic standards, but it was steady, and it went on day and night, week and month and year without end. The cascade refiners turned out a constant stream of ultra-pure, long-life isotope ingots, and the unmanned space ships came in a steady stream to the little five-mile chunks of rock, arriving empty, and departing with full loads.

It was a scene of never-ceasing activity, but soundless—without air—and the busiest components of the landscape, the reactors and refiners, remained out of sight. Equally invisible was the radiation range, except for a comparatively tiny seepage.

Of course, the seepage didn’t bother the robots, for their special sensory receptors—the instruments which Tinker called the “heads”—were in dummy sockets and not plugged in at the apex. Their usual sense organs, located in the torso itself, had what the manuals described as “Class I adjacent-band interference rejection.” In other words, they weren’t very sensitive.

But the heads, designed to pick up minute sparks from defective equipment, and used only for diagnosing breakdowns, were so abnormally sensitive that they were eventually certain to pick up constant static signals from the reactors.

That meant, of course, that they couldn’t be worn all the time. The robot “neural” system was almost inflexible but constant faint signals would derange it, confuse the robot reflexes and eventually lead to a condition that the manuals defined as “crystalline neurosis.”

Crystalline neurosis indeed! But Tinker knew what it meant in practice, at least. It meant that something had gone wrong that the robots themselves couldn’t repair, and that was why he and Drake were handily next door, sweating out their contract time in a well-insulated space house equipped with air and water purifiers, on Asteroid B.

The radio crackled in Tinker’s ear. “What’s the matter with that one?” the girl demanded.

Tinker looked up. The girl was standing over him, working on an overhead grouping of the circuits—except that she wasn’t actually working. She was staring out at the scene beyond the shed, where one of the robots was down on the rock, kicking feebly.

Tinker said, “Our excellent friend is busted. A part wore out, I suppose. We may as well watch, and see how they fix it.”

Scarcely a minute later two more robots appeared and moved purposefully toward the fallen one. As they advanced the two new arrivals tugged their heads free from under their arms, and shifted them to their broad metal “shoulders.” A slight twist, and they were no longer headless.

The girl said humbly, “Tinker, explain it to me, please? I know all about the manuals—I helped write parts of them. But it all looks so different out here in the field.”

Tinker said, “Glad to oblige. You’re familiar with central control—the computer that programs all the robots? Well, when one of them breaks down, the nearest adjacent unit gets a distress signal. Instantly our dutiful friends stick their heads on—just as those two did. And—well, look.”

The two robots had suddenly become mechanics. With incredible, expert swiftness they had their fallen companion in sections, right there on the rock. The tiny individual parts were passed before the region where their eyes would have been—if the “head” had possessed eyes—in a complex gesture which the girl was sure involved some sort of testing.

It took hardly a minute before one of the newcomers located the faulty part—a worn out thermocouple. The second quickly detached his head again, and somehow managed to open a section of it. Out of the cavity thus exposed came a duplicate thermocouple to replace the old one. In another minute all three of the robots had their heads off and stored once more. The damaged one, looking assured, immediately sprang to his feet, and resumed his interrupted task.

“Clever, isn’t it?” Tinker said. “Tool chest, stockroom, testing instruments—all in one.”

The girl said doubtfully, “But why do they have their own individual heads? I should think just a couple scattered around the asteroid would suffice.”

“Why does every Ford have a jack in the luggage compartment?” Tinker asked, “Isn’t it obvious? They’re built to be self-sufficient. And they just about have to be, Siria. This is a very small asteroid. Quite frequently Drake and I kick ourselves uncomfortably far off the surface, to where the artificial gravity in our suits won’t bring us back. The robots don’t even have artificial gravity, and if anything went wrong with them out in space, they’d have to repair themselves.”

“I see what you mean,” the girl said. “But are you seriously suggesting that those heads can handle anything that goes wrong?”

“No, of course not,” Tinker said. “Not by themselves, at any rate. They’re just testing equipment and so on. The brains—the repair patterns, if you don’t like your robot men so anthropomorphic—are in the central control system. Do you know,” he went on quite irrelevantly, “that you have beautiful eyes?”

She laughed after a moment. “It may have been three months since you saw a woman. But you haven’t forgotten the meaning of a smooth line. Let’s get back to work.”

A moment later a flicker in the corner of her eye caught the girl’s attention, and she glanced up, startled. Overhead a large black shape was blotting out a chunk of the skyful of stars.

Tinker laughed. “B,” he said simply.

She nodded, staring. It had been a growing mountain, off on the horizon far to her left, a cold asteroid Paricutin, getting taller by the moment. Now it had separated and was floating free. Even as they watched, it climbed higher in the sky, looking like some plunging hell-bomb above a city pin-pointed for atomic disaster on a tragically conclusive scale.

“It isn’t falling,” Tinker reassured her. “It’s just home sweet home—Asteroid Y-335 B.”

“I know it isn’t falling,” she breathed, drawing closer to him. “It’s just that I can’t get used to its being up there at all.”

Tinker sighed. “I have to get used to it because I’d be homeless if it disappeared. Atmosphere artificial, gravity equally plush-velvet. Time of revolution for the binary pair, seventy-five minutes. Population, two—John Tinker, probably lunatic adventurer, and George Drake, possibly dangerously sane rat.”

She glanced at him thoughtfully. “It’s easy to see that you don’t like Drake.”

“You haven’t met Drake,” he explained. “Anyway, it’s not as bad as it might be. There are, I’ll concede, certain physical comforts. The air is kept fresh, and the food is extremely tasty. The drinks taste good—even though they’re non-intoxicating. There is continual radio contact with women on Earth—also non-intoxicating. That’s why, Siria,” he went on earnestly, “I have been urging you to join our little band. You are intoxicating. Will you—”

“Tinker,” she said with reproachful insistence, “will you please keep your mind on business? Will you please—what’s that?”

The B asteroid was still hovering high in the sky but now a tiny black dot was moving out from it, precisely as the planetoid itself had separated from the horizon. They watched it wordlessly for a moment. They could see that it was expanding slowly, changing its shape as it grew. It shrank, and lengthened, dwindled, and swelled, but always its longest aspect was greater than it had been a moment before.

“Drake,” said Tinker proudly, “is a rank amateur.”

“An amateur?”

“At the jump,” Tinker explained. “We have jet-assists to get us from one asteroid to another if we need them. But if we aren’t in a hurry we jump. It’s just as safe, and far more comfortable.”

“But suppose you miss?”

“We never miss,” Tinker said with quiet dignity. But honesty made him add: “Anyway, it’s perfectly safe. We have to cut the artificial gravity in our bootsoles to jump—and if it looks as if we’re drifting off course we just switch it on again. But Drake’s a clumsy amateur. Look at the way he spins! Four or five turns a minute, easy.”

“And you?”

“One turn a minute, maximum.” He made a regal gesture. “Don’t applaud, please. Well—he won’t be here for twenty minutes yet. We might as well get back to work.”

It was nearer twenty-five minutes before Drake’s body, upside down, floated gently past one of the reaction buildings. He caught at an edge, righted himself on the fly, and then let himself drift gently down beside them. On the ground he turned on his bootsole gravitators and stood upright and at ease.

He took a deep breath.

“Greetings!” his voice rattled in their helmets, with an obvious attempt at geniality. “Tinker, you skunk, I heard you talking to our friend on the radio. Why didn’t you tell me she was a girl?”

“I always have been a girl, Mr. Drake,” said Siria.

“I don’t doubt it for a moment,” said Drake. “Well, so long, Tinker.”

Tinker looked at his colleague thoughtfully. “You aren’t by any chance in a hurry to get rid of me, are you?”

“Of course not, Tinker. Goodbye.”

The girl said, “Thanks for everything, Tinker. You’ve been a real help. Another hour and we’ll have the new circuits installed, so I guess I won’t be seeing you again. It really is goodbye.”

Tinker thought out loud, “It’s only been seven hours. Maybe I’ll just stick around and—”

“No, no,” said Drake hastily. “Don’t take unnecessary risks, Tinker. Radioactivity’s dangerous stuff.”

“Well,” Tinker looked rather desperately toward the horizon. “I’ll tell you what,” he said. “Your space ship’s gravity-stabilized, Siria. I’ll just climb into it for a while. I’ll be safe and insulated against radiation, and then—”

“Tinker,” said Drake reproachfully, “we’d love to have you stay. But I started the coffeemaker for you in the spacehouse. You know how unreasonable that gadget is. If you aren’t there in half an hour it will spatter coffee all over the kitchen.”

“Damn it, Drake,” Tinker remonstrated angrily. “I ought to wring your neck.”

The girl was laughing. “Really, Tinker,” she said, “I’ll be perfectly all right here with Mr. Drake. Go ahead before I start worrying about you.”

“Will you drop in for a cup of coffee before you go back to Earth?”

“All right,” Siria promised. “Now go ahead!”

Tinker glared at Drake, but no expression was visible through his partner’s faceplate. It wasn’t like the man to be gallant. From his long winter-evening reminiscences, extremely primitive lovemaking was more his style. Still—Siria was pretty well protected by the radiation field, if nothing else, to say nothing of the lack of atmosphere. It would take a genius even to get a look at her face under the circumstances.

And, Tinker admitted to himself, he was undergoing more radiation exposure than safety considerations could possibly sanction, especially since he had three months more to go on his tour of duty. Likely enough Drake was relying on his massive male personality to make an impression on Siria for some later occasion. “Okay,” Tinker said reluctantly. “But that’s a promise, Siria. See you later.”

Asteroid B was low on the horizon, but by careful manipulation of the bootsole gravitators Tinker could spiral after it. He took a little run to gather speed, cut the gravity and leapt boldly into space.

As he sailed away, spinning in the sedate pace on which he prided himself, he could see Drake and the girl turning toward the circuit sheds once more. He caught a few words of explanation from Siria to the man about the circuits, and then the bulk of Asteroid A came between him and the two and shadowed the radio waves. He knew that by the time they were in line-of-sight again, they would be too far from his helmet radio for their voices to carry.

By carefully timing the amount and direction of gravitator flow Tinker swung around in a spiral toward the spacehouse on Asteroid B. He made his corrections early, and as B ascended above the horizon he zeroed in with error-allowing caution toward the building where he and Drake lived.

He leaned back against his armor and relaxed in the void.

It was a wonderful feeling to float free from the tug of gravity, to sail gently upward while heart and lungs and brain relaxed completely. He stared drowsily at the hard, bright stars....

It was not, however, so wonderful that he could afford to fall asleep, and risk sailing so far past B that he’d never be able to return. He shook himself and kept his eyes open, watching the universe spin around and around while he whirled gently on his own axis.

“That lying skunk!” ranted Tinker. “He just wanted to get me out of the way!”

He stared in bitter fury at the cold and empty coffeemaker, which had not been left turned on! He should have known that the last thing in the universe Drake would ever think of doing was a favor for someone else.

He started the coffee and then surlily seated himself before the TV screen. A filmplay was coming through from Deimos Relay, but he was unable to concentrate on it.

He found himself seeing instead what he imagined to be the face of Siria Cottrell. He really was getting space-happy, letting himself become torn up over a girl whose face he had never even seen!

But it was curiously pleasant.

He glanced at his watch. He’d been gone exactly half an hour. Not more than an hour to wait, at most, before he’d be seeing her again. But he felt uneasy in an inexplicable way. Not so inexplicable, though, he realized. It was the thought of Drake alone with the girl that bothered him. Drake was an unmitigated scoundrel.

Most of the men the Company assigned to lonely outposts like Binary Y-335 were carefully picked volunteers. But there were exceptions, and Drake was one of the really bad ones. An ugly record of convictions for nine crimes. It was amazing that the authorities had accepted Drake’s petition for voluntary psychiatric treatment.

Of course, there was such a thing as pressure on the parole board, Tinker reminded himself, and it was quite possible such pressure had been applied. At any rate, the “voluntary dangerous labor” assignment after the psychiatry had turned out to be the same “high-bonus” job which Tinker had so eagerly volunteered for.

Anyway, even if there had been successful psychiatry, it was down the drain now. Three months on the lonely asteroid with Tinker had opened big cracks in Drake’s facade of adjustment. He had become more and more morose, spiteful, and selfish.

It would have been a difficult enough assignment for even a stable personality. But for Drake it brought to the surface his enormous instinct for selfishness—the world-hatred of the compulsive and rejected man.

Tinker found himself at the window-plate, staring at Asteroid A. But the buildings where Drake and the girl had joined forces were still beyond his range of vision. A few minutes later, however, they came into view and Tinker, no longer even pretending to watch the filmplay, began grimly hanging on to the eyepiece of the big telescope.

He scanned Asteroid A carefully. The streets were occupied—but only with the headless robots, still stalking around on their cryptic errands. The building that housed the great electronic brain looked empty.

But he found them at last.

They seemed to be walking almost arm in arm, in a sort of ungainly waltz. But, though the distorted perspective made it hard to see the pattern of that incredible “dance,” Tinker recognized it for what it was.

Drake was walking toward the girl’s space ship. And Siria, beside him, was bobbing aimlessly as his arm tugged her along. He was forcibly dragging her.

Tinker wasted no time in reproaching himself. He struggled into his space suit and was outside in a matter of seconds. There was a rocket launcher just outside, designed for quick emergency transportation from B to A.

He was facing an emergency now. He stepped into the rocketboots, cut his gravity, and pulled the switch. Almost immediately Asteroid A swelled to the dimensions of a celestial melon, mottled and light-rimmed in the void above him. Swiftly it grew larger, filling the entire viewscreen, becoming a variegated relief map of familiar design.

Ten minutes later he slammed against Asteroid A’s surface, braked a trifle by the bootsole gravitators, and guided by precision calculations and his desperate need to arrive at his destination in time.

He clawed his way upright just as Drake was lifting the girl to the hatch of her radiation-insulated space ship.

Drake saw him at once, and sprang toward him. There was no concealment now. Tinker knew what the cost would be if he lost. There was small chance that Drake would let him live any longer than he thought desirable. It would be easy to imprison him in the space ship and send it rocketing off into outer space forever. The flatbarreled, compact little gun in Drake’s hand made his intentions perfectly plain.

“Drop it!” Tinker yelled; and the moment’s surprise gave him the split-second he needed.

Drake hesitated only a tiny fraction of a breath. But drawing and aiming with space-gauntlets was slow work and before he could get the weapon into firing position Tinker was at his knees, bringing him down. Drake kicked out, swearing violently. The heavy boot caught Tinker in his middle, folding him up. He coughed and gasped and squirmed erect, clutching for the gun.

The slender metal rod wouldn’t kill him. It wasn’t built for that under any circumstances, and the heavy shielding of the space suit would ground most of the charge. But it would stun him at the least, put him out for minutes—and Drake would need only a few seconds to hack a hole in the delicate jointure between neck and shoulders, or the vulnerable spot at the armpits. Then the air in Tinker’s suit would go hissing out into the void, carrying Tinker’s life with it.

Drake kicked at him again, but he juggled the gun and dropped it. Without gravity of its own the weapon spun lazily in the air, hanging and floating slowly like a toy balloon. Drake clutched at it like a madman grabbing at phantom flies, but Tinker was there before him.

He didn’t try to grab the gun, only to knock it away. And he succeeded. It clattered against his helmet and bounced off, up and away—meters high and still going. The chances were good that it was gone forever, beyond B’s tiny gravity. At the least, it was out of reach for either Tinker or Drake for a good long while.

Drake copied Tinker’s tactics and butted the smaller man as Tinker had butted the gun. But Tinker anticipated the move. The moment his partner thudded into him he switched off his gravity. He went flying against the side of the ship and scrambled around the hull, kicking against it until the impact sent him flying back at Drake.

Both men were out of breath by now. But that was all. It was a crazy fight, Tinker thought, throwing himself at the other man again. The space suits were perfect protection against anything they could do to each other barehanded.

If one of them could have gained a moment to find a gun, a knife—even a heavy bar—the odds would have shifted in his favor. But barehanded, they were equal and invulnerable, like two giant herbivorous saurians thumping each other toothlessly over a luscious patch of weed.

They each had weak spots, of course. But they were hard to get to, except manually. The gloves were thin and flexible, by comparison, as they had to be. But both men were aware of that and were careful to keep their hands out of danger. The result was that neither Tinker nor Drake, however desperately they struggled and charged, could inflict decisive punishment. The only outcome, Tinker thought, breathlessly resentful, would be that one of them would drop of a heart attack.

But he was wrong.

Drake’s clumsiness won him the fight. He lunged at Tinker and slipped and wriggled free. But Tinker had caught him by the leg and whirled him around. Drake, panicky, kicked at Tinker’s sensitive hand. And Tinker let go. The instant he did so Drake went flying through the space above the incurious, busy robots, straight against the side of the space ship.

Tinker leaped after him, but he was too late. He struck the side of the ship and bounded away, and before he could right himself Drake was scuttling into the open hatch.

Tinker, abruptly warned, came hurtling back. But by now the hatch was closing.

Tinker leaped back a couple of yards and stared. What was Drake up to? In a moment he found out. The little ship, no more than five yards long, shuddered and bucked once at the touch of an unfamiliar hand on the controls.

And then it rose gently into the void and came at Tinker. Tinker flattened himself against the ground, and the ship missed him by a hair. But it was small and responsive. It stopped and whirled and came at him again. He could see Drake’s looming ugly helmet over the control board, through the forward view plate. He dodged again and stopped down his gravitators. He ran with zigzag, plunging strides.

But the ship swooped toward him, not fast, but with deadly persistence, twisting around the corner of a building after him, picking up speed on the straight-away. He tried to stay close to the building wall, but even as clumsy a pilot as Drake could put that little ship just where he wanted it.

Tinker dodged and ducked a fraction of a second too late, and caught a jolt from the vessel’s underbelly on his shoulder that sent him spinning into the wall. He rolled over, half dazed, to see the ship stop dead, and move back toward him with rapidly increasing speed.

The chances were very good that he would be crushed to death then and there.

There was a space in the building wall beside him. He scrambled through, just in time. The ship’s hull shook the supporting beams behind him.

Tinker stood up and looked around for some object that might serve as a weapon. But it was a hope that quickly died. He could see Siria lying, motionless, yards away beside another building, and the thought occurred to him that it was only a question of time before Drake would get back to her. The fear in his mind became almost unendurable.

There wasn’t much time for thinking. He felt a vibration in his bootsoles and looked up to see the prow of the ship slicing through the roof of the building.

There wasn’t any choice. He dodged behind a group of wiring panels, took a deep breath, and leaped for the girl. He dodged past the headless robots, who paid him no attention at all, and reached her while the ship was still methodically crushing the building he had just left.

Siria was stirring. Tinker dragged her hastily inside another building. He shook her to get her attention, then held a gauntleted finger up before his faceplate in an awkward “ssh” gesture. Miraculously, she understood him. Drake might not have the ship’s radio tuned to the helmet-talk wavelengths. But it was a circumstance he couldn’t count on.

Beneath the buildings was a partial network of tunnels, built mostly to serve as ducts for electric and communications cables which could not be left exposed to the radiation from the reactors and the cosmic rays. They had been enlarged in some parts to serve as storage space, and when Tinker hunted for an entrance he quickly found one. They were safe, at least for the moment.

“We can talk now,” Tinker said reassuringly. “The rock will ground our radio. How do you feel?”

Her voice sounded shaky. “I have a headache—that much I know. He hit me with a wrench.”

Tinker nodded thoughtfully. “It had to be something like that. You’re lucky he didn’t hit harder. But I guess he intended to spare you until he could get the ship safely off the asteroid.”

He could feel the girl shudder. “I’ve been pursued now and then,” she said after a moment, “but nothing like this. It’s a frightening thing, Tinker.”

Tinker said: “I don’t think it was just you, Siria. He’s crazy but—not that crazy. I think he’s in mortal terror of the law. I guess he thought it would be a good idea to take you with him, but judging from the way he’s acting now—” Tinker paused. They could feel the vibrations of Drake’s ship, still systematically destroying the debris of the warehouse. “I’m afraid he’s changed his mind,” Tinker went on grimly. “He’ll probably try to kill us both.”

“But why?” the girl asked.

Tinker explained, “He’s a criminal. He has three years to go on this asteroid before he’s technically free. I guess he can’t wait. You see, he’s never had a chance to get away before, not until you landed in your ship. The ship’s his passport. And consider the wealth here. These isotopes are worth a fortune on the black radioactives market. And your ship is a Company job, with radiation-retarded storage bins—everything he needs.”

The girl was silent for a moment. “Does he have to kill us?”

“I’m afraid so, Siria,” Tinker said gently. “If he leaves us alive, we’ll have the law on him in an hour, and the space patrol would nab him. He needs at least a day’s start. He can’t even destroy the radio on Asteroid B. If it doesn’t send an automatic check signal every ten minutes, the Company will think we’ve blown up and the patrol will be here anyway.”

Siria rested while Tinker made a scouting trip to the electronic-brain shed. From inside its complex array of circuit boards he could see Drake’s ship, now hovering motionless a few yards over the top of a building a hundred yards away. Tinker watched for a long minute, but nothing happened.

He had a worried expression on his face when he rejoined the girl and, though his countenance was invisible to her, she could hear the strain in the voice. “How bad is it?” she asked.

Tinker said, “Bad enough. He’s in a pretty favorable spot. So long as he stays in the ship, we can’t touch him. I’m afraid time’s working for him. The longer we stay here, the better off he will be. If we stay here more than twenty-four hours, we’ll die. The radiation could kill us in fifteen hours.”

She was silent for a moment. “I see,” was all she said.

“On the other hand,” resumed Tinker, more confidently, “there must be something we can do. Maybe we don’t know what it is, but there never was a tactical position so strong it couldn’t be attacked. At least we’ve got that factor working for us.”

She hesitated. “Tinker,” she said uncertainly, “did I understand what you just said? There’s a weakness in his position, and we don’t know what it is. We don’t know, but—it helps us?”

“Certainly,” said Tinker, his voice reassuring. “Consider all the things we might try. First, we could make a jump for the radio on Asteroid B. That won’t work, because he’d promptly run us down in the ship. Second, we could attack the ship with our bare hands. That’s out too, because we couldn’t do it any damage. Third, we could just wait here until he goes away. That won’t work, because we’d die of radiation poisoning. Fourth, we could—”

“Tinker!” cried the girl. “You’re cracking!”

He smiled. “Not exactly, dear,” he said. “There must be some weakness in Drake’s strategic position.”

“But we don’t know what it is. You said so yourself!”

“That’s true,” he conceded. “But you see, Drake doesn’t suspect that we don’t know. You’ll find that situation described in Clausewitz’s Tactics,” he added encouragingly. “Unless I made it up myself.”

Siria might have had her doubts about Tinker’s sanity, but she grimly followed orders. Most of her engineering knowledge was from textbooks and the drawing board, but she put her mind to practical mechanics and quickly erected the mechanism Tinker had specified out of spare parts in the storage buildings.

The machine glittered and sparkled. It towered higher than her head. It was rude and clumsy in construction, but it had a long, deadly-looking barrel that came out of its vitals and poked threateningly into space. And it did absolutely nothing.

She was staring at it dourly when Tinker scrambled out of the tunnel hatch behind her. He turned his radio volume down as far as possible and, his helmet almost touching hers, asked: “Everything all right?”

“I suppose so,” she whispered, “but—”

“Never mind. Any trouble with the robots?”

She shook her head. “They look the same as ever. But I’ve been staying out of sight, just as you advised, even if they are perfectly harmless.”

“They aren’t,” he said, surprisingly. “But don’t worry about it right now.”

He stood up cautiously and peered around. Drake’s ship was methodically cruising up and down the lanes of buildings, not particularly close. There were individual robots and groups wandering up and down, their “heads” under their arms in their accustomed fashion.

But they were slightly different in some respects now, since Tinker had made certain changes in the master pattern-sets in the electronic brain.

“Drake’s looking for us,” he reported to the girl, sinking down again. “That’s good. It shows he’s getting edgy. I don’t blame him. He thinks that once he takes care of us, he’ll be free. But the longer he waits the greater the chance of some wandering patrol vessel or freighter blundering in, for some message coming through from the Company that starts them wondering. So he’s irritable—jumpy. He’s desperately anxious to get away.”

“So am I,” the girl said.

“All right.” Tinker stood up again, took a last look. The ship was close at hand, but none of the robots were. Conditions would never be any better. “This is it, Siria,” he said, bending close. “In case anything goes wrong, I love you.”

A second later, trundling the imitation machine out into the open, he wondered just how much he had been deceiving himself. Not very much, he decided, almost incredulously. But then he didn’t have time to think for quite a while.

The main problem was to move the machine a substantial distance away from any building. He hadn’t moved it quite as far as he might have wished when he saw the nose of the ship come suddenly about and head toward him. Drake had sighted him.

Tinker gave a splendid five-second performance of the Courageous Ack-Ack Gunner, sticking to his weapon to the last. He tugged and strained and twisted dials, and sighted through tubes. It was almost too realistic to be safe, because he just barely managed to dive aside in time to dodge Drake’s ship.

It was hare-and-hound for several frantic seconds after that, but Tinker had picked his spot and he made it to one of the buildings and into the tunnels. Drake had learned his lesson about the futility of knocking down buildings. He hung irresolute for a moment, then drifted back toward the “weapon.”

Tinker stood watching half inside the tunnel for a long moment, with his heart in his mouth. Then, slowly, the hatch began to open.

Drake had taken the bait.

Tinker was through the tunnel and up beside the girl again in a new speed record for Asteroid Y-335 A. She was crouched behind a wall, as good as her word. He tugged at her, and the two of them raced through the tunnels again to the electronic-brain building.

“Faster!” he urged through the helmet radio. “We don’t want to run into any robots here!”

She gasped something in protest, but he didn’t bother to answer. Then they were scrambling up through the hatchway into the computer’s own building, and he breathed more easily.

“Now,” he said. “We wait. Drake’s following his script like a little angel. He had to take a look at that thing. If it was real, he had to know it, for we might have been able to build another.”

“I know,” said the girl, sobbing for breath. “But Tinker, what now? He’ll just get back in the ship, and we’ll be as badly off as ever.”

“Wait,” said Tinker tensely. He was feeling a reaction now; this was the key moment. He glanced beseechingly at the computer tubes, winking their little electronic messages. He said, with a voice that shook slightly, “I don’t like playing God. I’ve never known what it was deliberately to take a human life before.”

“Life?” the girl demanded. “When did you take anybody’s life?”

Lights flared up in the computer brain in a blaze, and died again. They flared more brightly, erratically; and the machine seemed to tremble slightly.

Tinker sighed a long weary sigh. “Just now,” he said, and began to rip out the additional control circuits he had so frantically installed. “We can go up now. Drake’s dead.”

Tinker made the girl wait in the shed for a moment. Then he came back, walking slowly, and said, “All right, Siria. Let’s go.”

She followed him in silence to the space ship. There was no sign of Drake, nothing but the meandering robots, their heads tucked underneath their arms. When they were in the ship and Siria looked back at the asteroid they were leaving, she thought she saw—

“Tinker,” she said in a voice that shook. “Look back there, where the ship was—”

He said somberly, “Yes, Siria. That’s Drake. The robots took care of him.”

“Impossible!” she said. “The robots can’t conceivably harm a human being! Every control circuit ever designed has—”

“Has its weaknesses, Siria,” Tinker said. “I made a few changes. No—don’t interrupt. I couldn’t make them attack Drake. But I could change their repair instructions. I put in a new circuit describing a new repair problem—crystalline neurosis.

“It was easy enough, for the basic condition was already in the memory tanks. Robot’s head stuck on shoulder. Too many static bursts accepted as repair signals, with a resultant neurotic behavior pattern on the part of the robot affected. That was all standard. The only change I made was to describe a new type of robot.” He swallowed. “One that looked like—like a human being in a space suit. I knew about it, so I kept us out of sight. Drake didn’t.”

“Tinker!” cried the girl.

He nodded. “So they—repaired him. And the way to repair a stuck apex-mounted receptor, of course, is to take it off and dismember it.” They were silent for a moment while Tinker slipped the little ship into a landing next to the spacehouse. Both were looking gray.

“The computer knew something was wrong,” he said, “when they got the—the apex-mounted receptor apart. It wasn’t a standard design. So it blew fuses; and that’s when I knew it was over.”

He helped her wordlessly out of the ship, through the landing tube, into the spacehouse, and tripped the emergency distress signal that would bring the space patrol and the Company’s ships arrowing toward them through the interplanetary night.

And then, for the first time, he pushed back her helmet and looked at her.

“Beautiful,” he said. “I knew you’d be beautiful.”