“What did you do to his ship, though?” Ariel asked, exasperated.

“Blow up. All time we waiting in orrbit, we were making explosivess. Carbonite recipe in Dr. Avery ship data bank. I know enough chemistry to add oxidizer. Had to use food synthesizerr feedstock, but only one of me to feed, and I ssmall.”

The robots had no doubt needed carbonite for the building of Robot City. Derec knew generally how it was made: it was a super form of black powder, using activated charcoal saturated with potassium nitrate or sodium nitrate. Since the carbon was nearly all burned up-it approached one hundred percent efficiency and was therefore nearly smokeless-carbonite was about ten times as powerful as TNT.

“Even so, it would not worrk if Aranimass had not panicked and Jumped. But he could not know what wass happening.”

Derec nodded, immediately wished he hadn’t; the room seemed to spin. “His panic is understandable,” he said.

“Are’ ou all right?” Wolruff asked.

“No, but I’m not getting worse. I mean, I’m feeling no worse than before the battle.”

Ariel broke in to explain about the chemfets, and Wolruf was concerned but unable to help. She knew nothing of robots, nor did any race she knew of, save humans.

“I hope ‘ou will be well,” she said, but clearly had her doubts. She seemed shaken by the idea of this invasion.

Derec thought of it as a disease, and at least had the hope that the chemfets were programmed with the Three Laws.

“Shall we go?” he asked. He turned and found Mandelbrot looking at him.

“What do you intend to do about this infestation?” the robot asked.

“Go to Robot City and either turn the problem over to the Human Medical Team or seize Dr. Avery and force him to reverse it-or both,” said Ariel.

“I see. I can think of nothing better, for I do not believe that the medical and/or robotic resources of Aurora or the other Spacer worlds would be adequate to the task of eradication of chemfets,” Mandelbrot said. “That then must remain purely as a final resort.”

“Rright,” said Wolruf. “We go find Dr. Avery. He worrse than Aranimass!”

The next step was to explore the alien ship. They cast off from Wolruf’s Star Seeker and jetted lightly toward one of the larger, more intact hulls. They carried clubs, and Ariel a knife from the galley, but they found it airless and had little fear of survivors. There were none, as it turned out. Nor were there all that many bodies.

“Aranimas musst have sounded the recall and called them to the main hull,” Wolruf said. “They would be valuable to him, of courrse.”

Still, a good number of innocent Narwe-and not-so-innocent starfish folk-had died in the battle. They found nothing of immediate use in the first two hulls, and became depressed.

“We must have air, if nothing else,” Mandelbrot said. “ And we should also find organic feedstock for the synthesizers. It is, you tell me, five Jumps to Robot City. It will take at least three weeks, and then there is the final approach, and a reserve against emergencies. This hull will not hold air for three days. It can be patched up more, but probably not enough to hold air for more than a week. We will need four complements of air, and even so, I must spend every moment patching till the Jump.”

“You’ll be patching after every Jump,” Derec said grimly.

Mandelbrot was right. They returned to the search, though the hulls were getting far apart now.

The next hull had been one occupied by the starfish folk, and they immediately gave up hope of finding air here; the strange aliens breathed a mix containing a sulfur compound that Wolruf called “yellow-gas.” On the way out, though, they found a robot.

At Ariel’s cry, Derec shook his head and took a deep breath. The robot, when he came into the open chamber where she was, seemed a breath of sanity in unreality: the shot-up spaceship, in free-fall and airless, was like an Escher print of an upside down world. The body of one of the starfish folk was stuck to one wall, a vicious-looking energy piston in one tentacled grip. Ariel and the robot were spinning slowly in the vacuum, drifting toward a bulkhead. She had leaped to seize it.

“It’s dysfunctional,” she said.

Timing his moves with hers, he intercepted them at the bulkhead and they turned their lights on it. It made no move, but whether it was speaking or not, they could not tell.

Mandelbrot entered while they were examining the robot’s body. “Energy scoring on the head, and fuse marks here and there, mostly on the body. It looks like the starfish over there shot it up during the battle.

“How did it come to be in the ship?” Ariel asked.

“Hmm. I suppose Aranimas must have come upon it somewhere and captured it,” said Derec.

“Where could he have found it?”

Derec considered. “Possibly it’s one he found at the ice asteroid. But I doubt it. He was desperate for me to make him a robot. He’d have given me all the parts he had.”

Mandelbrot fixed his cold eyes on the damaged robot. “This is a robot from Robot City.”

“Yes.” The design style was unmistakable to the trained eye.

“Let’s get it into air; maybe it’s trying to speak,” said Ariel.

But back in the Star Seeker it lay as inert as before. Removing his spacesuit, Derec got out the toolkit and looked at Mandelbrot. The prospect of work on the robot made him feel better than he had in days. A matter of interest. They quickly learned that power to the brain was off. Reenergizing it, though, did no good.

“A near-miss from an energy beam might well cause brain burn-out without visibly damaging the brain,” said Mandelbrot.

The positronic brain was a platinum-iridium sponge, with a high refractivity; it wouldn’t melt easily. But the positronic paths through it were not so resistant.

“So we can learn nothing from questioning it,” Derec said, dejected. “Wait a minute. What’s this?”

Clutched tightly in its fist was a shiny object. A shiny rectangular object.

“A Key to Perihelion,” said Mandelbrot expressionlessly. “

Aranimas would have taken it away from the robot if he’d known it had one,” said Ariel. “I wonder what the robot was doing with it?”

“We’ll never know. Maybe it took the first moment it wasn’t under observation to try use the Key. And the starfish caught it in the act.” Derec gripped the Key and pulled it out of the fist. Instantly he knew it was different.

“It feels like two Keys built together!”

“It is,” said Mandelbrot, peering at it. “One, I suppose, to take the robot from Robot City. One to return him to Robot City.”

“Which is which?” Ariel asked.

Derec and Mandelbrot spent a few minutes determining that. They found that one Key had a cable plug in one end.

“I see,” Ariel said, when they showed her. “A tiny cable, with five tiny prongs. It must be for reprogramming. I don’t know what would plug into it-”

“Something like a calculator,” said Derec, “to enable one to input the coordinates of the destination. “

The other Key had no provision for changing its programming, and was therefore set permanently on Robot City.

“Not that it does us any good,” said Ariel wistfully. “It’s initialized for a robot. Too bad; we desperately need to get to Robot City, especially Derec. And only Mandelbrot can get there.”

“That is true; Derec must go to Robot City soon, and the Key is better than three weeks in a ship, even if the ship did not leak,” said Mandelbrot. “I will take you there, Derec.” He wrapped his normal arm around Derec, half carrying him.

“What about us?” Ariel cried. “This ship is no safer for Wolruf and me.”

Mandelbrot’s mutable Avery-designed arm was already stretching into a long tentacle. “That is correct-it is very likely that you and Wolruf will die if you do not accompany us,” he said. “Therefore, I shall have to take you all.”

The tentacle coiled about Ariel and Wolruf and splayed out into a small hand at the end. “The Key, if you please, Derec.”