Excited by the information, revived by the challenge of a scientific dilemma, Avery seemed more and more his old self. He now stood by a desk, his fingers drumming in a fast, steady rhythm. His other hand kept touching his long white hair or bushy moustache. His eyes glowed again.

When Derec had related all he could remember, Avery balled up his hand into a fist and rammed it hard against his upper thigh.

“That’s it!” he cried. “That must be it!”

“I hope you’ll let me in on it, since I’m thoroughly confused now.”

“Bogie-the robot posing as Bogie is a Silverside.”

“You mean Adam or Eve? Really, I don’t think so. They weren’t even here when things started to go wrong. They were with me on-”

“I don’t mean literally Adam and Eve. I mean Silverside generically. There is another of these robots like Adam and Eve somewhere in Robot City.”

“Another one?” For a moment, Derec was appalled at the prospect of a third mischievous robot to contend with, but then of course, he said to himself, I’ve been contending with it for days now. “You mean it was being Bogie because it was able to change into his shape, to imprint upon him?”

Avery nodded and smiled oddly. “I guess we’ve got, as well as Adam and Eve, Pinch Me.”

Derec wondered if the doctor had slipped back into madness. Avery saw his son’s confusion and quickly explained about the children’s riddle he had tried out on Adam.

“Adam never really understood it. I tried to tell him it was just a joke, but he didn’t catch on.”

“I know what you mean. I’ve spent hours attempting to make Mandelbrot understand what humor is all about. But what really is our Pinch Me? For that matter, what are the Silversides?”

“They’rre demonss, ‘u know,” Wolruf said from the floor. She had been intently listening to the conversation. “‘U should lock them up and hide key until they grrow up. That iss my opinion.”

“I agree, Wolruf,” Avery said. “I’d like to get them into a cell and take them apart, see what makes them tick.”

“Don’t ‘u tell Ariel that. Rememberr what she said about dancerss.”

“Yes, that’s good advice, Wolruf.”

Derec had no idea what they were talking about, but, with so many immediate problems to deal with, he decided not to ask questions about it.

“Father, you said you had an idea who the Silversides are.”

“Yes, and I have a hunch I’m right. Sit down.”

“I’m too nervous-”

“Sit down!”

The tone in Avery’s command was so authoritative, Derec decided there must be a good reason for the order. He pulled up a chair and sat on the edge of it.

“I hadn’t wanted to talk to you yet about your mother, Derec. If I could avoid it, I’d never tell you about her. Unfortunately, circumstances now make it necessary.”

Derec realized why his father had told him to sit down. He felt as if the air had been knocked out of him. What could his mother possibly have to do with the crisis on Robot City?

Avery started to pace. His fingers kept busy as he walked.

“I’m not going to tell you her name. You can dream that, if you want. Suffice it to say that, like me, like you, she was, is, a roboticist. A very good one, the only one who could really challenge me. Perhaps it was, in fact, competition that kept me going, made me succeed, a competition that continued even after she left me.”

Wolruf was sitting up now, apparently to hear Avery better. She looked improved. Her eyes were clearer, and a sheen had returned to her fur.

“When I came back here and found the city deteriorating,” Avery continued, “I knew that somebody or something was behind it. It wasn’t until I had the long talks with Adam that I began to suspect that there might be a third robot like him in the city. However, until our little talk, Derec, I wasn’t sure. Now the evidence seems clear to me. There is another robot, one like Adam and Eve, and the creator of all three of them, I am positive, is your mother.”

That little piece of information really stunned Derec. He had to struggle to speak again.

“But how can you be so sure they come from her?”

“I admit there is some intuition involved, but it’s intuition supported by logic. The Silversides and, presumably, our mysterious controller can only be the work of a robotics expert as skilled as I. That isn’t ego speaking. There just simply isn’t another roboticist as meticulous and creative-and that includes all the incompetents at the Robotics Institute on Aurora-as I am. Except for your mother.”

Avery stopped to observe the effects of his words upon his son. Derec knew he was not disguising his emotions even though he very much didn’t want his father to see them.

“I am projecting her intellectual progress, of course. It’s been a long time since I’ve seen her. At that time she was not yet my equal, especially in the fields of positronics and integrals, but in the years since, working in isolation, she may have come up to my level. I don’t like admitting that, but she is younger, and in some ways I’ve slowed down. Plus, I’ve channeled my activities into the planning and development of robot cities, while she has been able, apparently, to concentrate on robots alone. Even knowing her skills and intelligence, these new robots represent an achievement that takes my breath away. Does that seem strange to you, son? That the great egotist can indeed give credit to someone else? You’re thinking that, I can see.”

“Have you added telepathy to your considerable talents?”

Avery laughed abruptly. “You may be a chip off the old block after all. That sarcasm was worthy of me. Wonderful!”

“Why is it that your praise sounds like an insult?”

“That’ss enough,” Wolruf interjected. “You two can have yourr silly arrgument laterr. There’ss much to be done.”

Avery nodded toward Wolruf. “She’s bossy for an alien.”

“I like that in aliens,” Derec said.

“Pleasse,” Wolruf said.

“All right,” Derec said. “Assuming that my mother is behind all this, what’s she up to? Why develop this new kind of shape-changing robot and then dump individual ones on different planets?”

“I can only speculate about that.”

Avery resumed pacing on the far side of the room. Derec paced a shorter path on his side. Wolruf was amused by the resemblances between the two men when they were pacing.

“What it might be is that your mother always had a special interest in anthropology. She could go on for hours about tribes, customs, rites, that sort of bilgewater.”

“You don’t put much stock in anthropology?” Derec asked.

“Oh, it’s all right, just not in my sphere of interest. I’m a creator, a builder, and I like to stay by myself. Going out and observing sentient creatures go through their dull, daily routines, and analyzing the meanings of courtship and aggressive rituals just simply isn’t my line. It’s a useful minor science, where you can showboat by delivering solemn conclusions without much hard evidence, but it’s for people who are butterfingers in a lab. On the other hand, your mother thought it was fascinating to study cultures, and she’d go off for weeks and months to take a peek at some social grouping or other. She told me I was an old fuddy-duddy whenever I said anything the least bit derogatory about her precious anthropology. I suppose her scorn may have contributed to my present antipathy toward the field.”

“But I don’t see how anthropology applies to the new-styled robots.”

“Well, seems to me two factors particularly are clues to the anthropological nature of her experiment. One is that the Silversides seem to have come to consciousness with the urge to define and discover humanity, which they are further convinced is the highest intelligence in the universe. But she has deprived them of any real information about what humans are. Therefore, as you’ve described it, whatever kind of sentient being they discover, they almost desperately try to find its humanity.