If he were to release the robot from its instruction block and order it to move against Aranimas, that would create a Second Law obligation to break the First Law. His careful adjustments might come apart under the stress, and the robot would freeze up in a way Derec would not be able to repair.

He did not want to take that risk. It was much more straightforward for the robot to act in obedience to the First Law than in defiance of it. But that meant it was necessary to provoke Aranimas into an attack.

“It looks like a failure of the volitional initiator,” Derec double talked. “If two contradictory impulses reach it on the same pulse, it can set up a standing wave in the oscillator. It’s almost always the owner’s fault. What did you ask it to do?”

“I did nothing wrong, I was explaining the functions of the equipment in this section when its hand began to twirl foolishly that way.”

“Don’t lie to me,” Derec said. “I should have known that a race as backward as yours couldn’t cope with sophisticated machinery-”

“You are worse than the Narwe,” Aranimas snarled. “You do not have the good sense to know when you are in the service of a true superior.” As he spoke, his hand moved toward the gap in his robelike blouse.

“Aurora!” Derec shouted.

But the robot had begun to move even before Derec uttered the word, the First Law overcoming the strictures of the instruction block. The race between Aranimas’s reflexes and the robot’s was no contest. Before the stylus had even cleared the folds of Aranimas’s robe, the robot had grabbed the alien’s wrist with its right hand and plucked the stylus from his grasp with its left.

“Release me!” Aranimas squalled shrilly. He squirmed and fought, but could not free himself from the grip of the single mechanical hand.

“I cannot allow you to harm Derec,” the robot said.

“You are my servant. Obey my orders! Release me!”

“No, Aranimas,” Derec said, stepping forward. “Alpha is my servant, and always was.” Then he called back over his shoulder, “Wolruf! You can come in now!”

Retrieving the stylus from the floor, Derec turned it over in his hand. There were no obvious switches or controls on it. Holding it the way Aranimas had, Derec pointed it at the alien. Aranimas remained unaffected.

“My own weapons cannot be used against me,” Aranimas said with stiff pride.

“A very clever management technique,” Derec said. He reached into the tool clutch and retrieved the little toy he had made earlier that day. Attached to a small pressure bottle half full of mustard-yellow liquid was a miniature pump salvaged from the disabled robot. “But I have my own weapon.”

As Wolruf joined him, Derec pointed the pump’s outlet valve at Aranimas and pressed the switch. A fine mist blasted from the tiny opening and caught the alien in the face.

A human would have gasped in surprise. Aranimas lunged for the aerosol with his freehand and nearly got it, his arm span being almost equal to the makeshift device’s range.

But a moment later, a reddish liquid began streaming from Aranimas’s eyes, and the skin of his face seemed to pucker. He went rigid and reached high in the air with his free hand, the fingers curling as though grasping for something, the ropelike muscles of his arm and shoulder visible under the skin for the first time. As the aerosol began to sputter, the alien’s eyes closed, and his arm dropped limply to his side.

“Release him,” Derec said, thumbing the switch. The robot’s hand opened, and the alien crumpled to the deck and lay there motionless.

“I-detect-no respiration,” the robot said haltingly.

The robot’s speech impediment was a warning sign to Derec. I should have warned it what was going to happen, he realized belatedly. “He’s not dead,” Derec said. “His system has received a poison shock, but he will recover.”

“I-will try-to integrate-”

“Alpha-analyze the situation. This is Aranimas’s ship. He had all the advantages. He could have done a hundred things to stop us and we’d never have known until it was too late. He had to be neutralized.”

“I understand-and accept.”

“Are you all right?”

“I detect a moderate disturbance-in my brain potentials which I attribute-to witnessing violence against an intelligent-being-not-a-human,” the robot said, its speech gradually returning to normal. “The disturbance is abating and I do not believe that it will affect my functioning.”

“Good,” Derec said, dropping the spent aerosol on top of the tools. “What did you find out?”

“We are approaching an independent free-flying space station.”

“Frost,” Derec said emphatically. “I was hoping he’d take us right in to one of the Spacer worlds. How much time do we have?”

“I am unable to accurately estimate our arrival time. However, I did determine that the ship’s crew is presently at the lowest level of alert.”

“So we probably have more than a few hours,” Derec said. “Has Aranimas been in contact with the station?”

“Not that I am aware of, sir. This vessel does not appear to have hyperwave communications-only simple carrier-wave radio.”

That agreed with Derec’s experience on the asteroid, but it raised a puzzle. How had the aliens found the asteroid? Derec had assumed along with Monitor 5 that they had intercepted the distress message sent on his behalf. But without a hyperwave viewer, that was clearly impossible.

Perhaps Wolruf could shed some light-but it would have to wait. “Okay. What about the key? Do you know where it is?”

“Within limits. I believe it is concealed beneath one of the deck tiles of the command center.”

The last time he had been in the command center, Derec had been in too much pain to pay attention to his surroundings. “Let’s go see,” Derec said, starting off. “How did you find it?” he called back over his shoulder.

“Aranimas showed the key to me and questioned me about it,” the robot said. “When he left with it, I was not able to see precisely what disposition he made of it. However, the time he was gone limited the radius of concealment to this deck, and the sounds I heard were consistent with the removal and replacement of a floor tile.”

They reached the command center then, and Derec saw that the deck was a mosaic of several hundred hexagonal metal tiles the size of a dinner plate. The surface of each tile had a pattern of small holes, but there was no obvious fingerlift-in fact, no obvious way to lift an individual tile. All six edges were flush with the adjoining tiles.

“Any idea where I should start?”

“The strategy of concealment would argue against obvious positions such as the center and corners. Beyond that, I cannot say.”

“You can’t detect it under the deck? It’s not giving off some kind of radio signal, or generating a magnetic field?”

“Not that I am able to detect.”

That, too, was consistent with what had happened on the asteroid. If the key had declared its presence in any measurable way, the robots’ scans would have turned it up long before the raider ship arrived.

“All right,” Derec said slowly. He turned to Wolruf, who had been a silent spectator since joining them. “We need a place to lock up Aranimas.”

Wolruf glanced nervously back toward where they had left the Erani. “Therr arr some lockers outside, on the side passage, which would be large enough-”

Derec nodded. “Alpha-pick up Aranimas and go with Wolruf. She will show you where to put him. Wolruf, make sure it’s something Aranimas can’t open from the inside. Then both of you come back here.” He caught the look of apprehension in Wolruf’s eyes and added. “I know-you don’t like the robot.”

“Maybe ‘u surprise Wolruf like ‘u surprise Aranimas.”

“I promise you, it’ll be all right,” Derec said, patting the caninoid’s arm. “No surprises. I’ll be waiting for you here.”

When the robot was gone, Derec lowered himself to his hands and knees to examine the holes in the tiles. They proved to be tapered pits barely a half-centimeter deep. There seemed to be no way of hooking anything into one to lift the tile. Derec wondered if he would have to build some sort of vacuum clamp before he could locate the key.