“Hi,” said Alpha. “I was able to obtain a very small spacecraft and trace the source of the asteroid-disassembling operation to this planet. Wolruf accompanied me. More recently, I was detained by a robot search team and brought here.”

“Spacecraft?” Derec suppressed a giggle of delight and caught Ariel’s eye. “And Wolruf, too. How is she?”

“She is recovering from a difficult trip.”

“Recovering?” Ariel said. “But she’ll be all right?”

“Yes.”

“I’m glad,” said Derec. “We’ve worried about her. We’ll want to see her when we can. What about the spacecraft? Does it still work? And is it here and available and all that?”

“Yes.”

“Step out of line, Alpha.” Derec turned, grinning to the medical team. “This is not Jeff. I put Alpha together myself.”

“Hi, Alpha,” said Ariel, bouncing on the balls of her feet in excitement. “I’m real glad to see you. But why did they stop you? You have a comlink, don’t you.”

“Greetings, Katherine. My comlink was originally set at a slightly different frequency. I altered it but was detained anyway, I believe for having an anomalous comlink.”

“I’m Ariel Welsh now.”

“I do not understand,” said Alpha.

“Not now, not now. We’ll catch up with each other later,” said Derec. “For the business at hand, we’re down to four,” said Derec, looking over the others. “Research 1, were you able to begin testing, like you said?”

“Yes. According to our standard maintenance scanning procedure on their bodies, all four are in good condition, other than their common lack of functioning comlinks. Their heads have not been scanned. The two speaking robots have given identification that has been verified by the central computer. Their comlinks simply malfunctioned.”

“Dismiss them,” said Derec. “Alpha, you stay right here until further notice.”

“Report to the nearest repair facility,” said Research 1.

The other two robots left.

“So.” Derec stood in front of the two remaining robots, looking back and forth between them. “One of you is almost certainly Jeff. Unless you’ve fallen asleep, which I really doubt under the circumstances, you can hear me and you just aren’t letting on. Well, we’ll be right back.” He turned away, then paused to grin over his shoulder. “Don’t go anywhere, now. You’ll give yourself away.”

“Surgeon 1, you stay and watch them. Research, you and Ariel step outside with me for a minute.”

Derec paused in the hall, but Research 1 shook his head. “This is not sufficient for privacy. If you want to talk privately, we must go into another room and I will create sonic camouflage. Do not forget that Jeff has robotic hearing.”

“Lead the way.” Derec could hardly keep from dancing around with joy. Alpha had a working spacecraft somewhere here-once he and Ariel had smoked out Jeff, they could turn him over to the robots and take off. As they followed Research 1 into another room, he saw the smile on Ariel’s face and nudged her playfully with his elbow. She elbowed him back, a lot harder, but still grinning.

They entered what was obviously the facility’s operating room. Research 1 flipped a switch on some sort of scanning apparatus and a faint hum came on.

“They will not hear us. What do you wish to discuss?” Research 1 asked.

“They?” Ariel asked, “I don’t get it. One of them is an inoperative robot, isn’t he?”

“Immobile is not necessarily inoperative,” said Research 1. “We must be cautious.”

“Exactly,” said Derec. “Here’s how I figure it so far-correct me if I’m off. Jeff saw us coming in time to order another robot to freeze, and probably to follow only his instructions to activate again. I did basically the same thing with Alpha once. However, in order to hear Jeff’s instruction to reactivate, the other robot has to maintain hearing sensitivity and at least some mental activity. Right?”

“Correct,” said Research 1.

“What about a shortcut?” Derec asked. “Can’t you just scan their heads and find out which has the biological brain in it?”

“No,” said Research 1. “In constructing his special cranium, we used materials that would be extremely resistant to the entrance of any forms of energy, as well as to physical impact. Turning up our scanning beams to a strength that would penetrate his cranium would endanger the brain inside.”

“Hold it,” said Ariel. “You could use your normal scanning beam, and when you get a reading for one positronic brain and one null reading, we’d know by elimination.”

“We dare not,” said Research 1. “The cranium was tested before use, but not with the human brain inside. Even the normal scanning beam could be dangerous. The First Law does not allow us to take a risk of this magnitude.”

“All right. Somehow, I’m not surprised.” Derec sighed.

“The Laws of Robotics still hold precedence on them, too, though,” said Ariel. “I assume our tests will still work-won’t they?”

“Yes. They are based on the following,” said Research 1. “If Jeff had a positronic brain, he would have to obey the Laws-for instance, if one of you were in danger, he would have to save you. However, as a human, he could allow you to come to harm if he wished.”

“The problem,” said Derec, “is that Jeff knows the Laws and can masquerade as a robot.”

“We also don’t know what he told the other robot,” said Ariel. “If the other robot knows that we are setting up tests, then he won’t believe we’re really in danger and he won’t have to obey the Laws, either. They’ll still behave the same way.”

“Let’s get started and see what happens,” said Derec. “We’ll go in order, with tests one, two, and three.”

Derec and Ariel went back into the room with the suspect robots. The medical team had to leave, accompanied by Alpha, in order to avoid confusion. If they did not respond according to the Laws, the real robot would see it was a test; if they did respond, they would get in the way.

“I’ve had it with you,” Derec was yelling at Ariel. “You’re crazy.” He turned toward her in front of both robots.

“Oh, yeah?” She demanded. Then, according to their agreement, she swung back her fist and punched him in the stomach.

Even though he had been expecting the blow, Derec doubled over from the impact-partly from her very solid punch and partly as an act. Both robots jumped forward, no longer frozen in place, and pulled them apart. If one had been a shade faster, he couldn’t tell.

“Let go of me! Him, too!” Ariel shouted, as they had prearranged. Both robots obeyed, but remained between them, close enough to prevent more violence.

Derec, gasping for breath, looked up and found that they had both apparently deactivated again. It was time for the second test. He caught Ariel’s eye, saw that she was ready for him, and leaped at her throat as if to strangle her.

Instantly, both robots grabbed him in their powerful arms and held him fixed and helpless.

“Let go of me,” he ordered.

Neither one let him go. Now that the violence had been repeated, the First Law was going to remain in force over the Second, until they judged that the threat was over.

“You,” Ariel ordered, tapping one on the arm. “You go stand in the hall. The other one will keep me safe here. And you-Derec won’t hurt me right now. I know that. You can stand close if it makes you feel better, to stop us again if necessary.”

When both robots had complied, Derec and Ariel spoke amiably to demonstrate that the immediate threat of violence was over. Then the robots allowed them to retreat to the O.R. once again to consult with each other.

“Jeff’s pretty good,” said Derec. “He was right with the real robot every second-whichever one it was.” He grinned. “You’ve got a pretty good punch.”

Ariel shrugged. “Well, you said it should be the real thing. But now we know a little more. Direct application of the Laws activates the real robot, but only as long as the Laws apply. Then he freezes again, like Jeff ordered him.”