Derec’s eyes flicked left and right as he took in the formula. Janet watched his brows furrow at the nonstandard notation-notation she had devised herself to describe a nonstandard idea.

A shadow darkened the doorway behind his head, and a thin, dark-haired girl entered the room. Ariel Burgess. Janet had known she was traveling with Derec, but it was intuitive knowledge only. She wasn’t prepared for the shock of actually seeing her son’s lover so casually enter the picture.

“Wipe that off his desk!” Janet ordered, snatching her memcube from the reader in the same motion. She watched Derec’s face slip from puzzlement to frustration, then he heard Ariel and turned to ask her, “Did you do that?”

“Do what?”

“Put that formula on my desk?”

She came up behind him and looked over his shoulders. “What formula?”

“It disappeared when you came in. I don’t mean on the computer, either; it was molded right into the desktop.”

Ariel looked just as puzzled as he had. “No, I didn’t do anything like that. I was out in the living room reading. I heard you talking with someone and I came in to see what you were doing.”

Derec nodded. He looked at the desk, then up at Ariel again. “I’ve been trying to find Avery and the robots. I think he’s hiding out with them, probably trying to take them apart now that they’re locked up again. I think I’ve tracked them down, though. Want to come along and see?”

Ariel shook her head. “Doesn’t sound like it’s going to be much fun if that’s what’s really going on. You’ll probably just get in a fight with him. “

“Probably will.” Derec sighed. He turned back toward the desk, looking one last time for the phantom formula, and switched off the computer. Janet’s view didn’t even flicker; she watched Derec stand, put his arms around Ariel, and hug her tightly. She nearly ordered the computer to stop watching when they kissed, but her curiosity was too strong.

She wished she had, though, when Derec murmured softly, “Frost, why couldn’t I have had normal parents?”

Avery was watching the microscope monitor when the alarm went off. Someone had stopped in front of his laboratory door. He cursed at the interruption, cursed that it had happened now, of all times. He was just beginning to understand the changes Janet had made in the robot cell morphology and how those changes might affect the way they combined to make macroscopic structures. He didn’t want to deal with Derec just now, Derec and his whining about ruining his mother’s experiment. He knew that’s what Derec would say. He knew what he would say in return, that between them he and his mother and her stupid experiment had ruined just about everything he, Wendell Avery, had ever done, and that it was about time he turned the tables; but he wished he didn’t have to get into all that just now. He had better things to be doing.

Well, he supposed he didn’t have to stick around for it if he didn’t want to. It would take Derec a few minutes to get through the locked door; by then he could be long gone.

He picked up the sphere of undifferentiated robot material that had formerly been Lucius’s right leg, switched off the microscope, pocketed the memcube he’d been storing data in, and strode to the wall adjacent to the one with the door in it. “Make another doorway here,” he said, and as soon as it formed he stepped through into the next room beyond his lab. “Remove the doorway,” he ordered.

The room was an empty box with a single door opening out onto the slidewalks. Avery went to that door, eased it open a crack, and peered out to see if it was, indeed, Derec. The door made no noise that Avery could hear, but the figure in front of his lab turned as if startled by a sound, then immediately turned away and rushed off down the slidewalk, running at a speed that took him to the intersection with a cross-corridor in less time than it took Avery to shout, “Hey! Stop!” The figure turned left without slowing and vanished from sight.

It was a robot, then, one with prior orders. But the glimpse Avery had gotten of its face hadn’t suggested a robot at all. It had looked quite human.

Had Derec reprogrammed one of the city robots to take on a human appearance? They could do it if ordered to. But why would he have done that? Avery knew Derec; if he had found Avery’s lab he would have simply come here himself.

Who else could it have been, though? Neither Wolruf nor Ariel would have sent a robot to scout for them, either, and that exhausted the possibilities. There was nobody else on the planet.

Unless…

He shuddered at the thought. It made sense, though. She’d been on the other two planets they had visited, planets that had each been home to one of her infernal robots. She had left one of them here as well-it wouldn’t be surprising if she had come to check up on it.

Avery looked down at the lump of robot material in his hand. He felt a twinge of guilt steal over him, but he fought it off, scowling. She’d disrupted his experiment; he had every right to disrupt hers.

But it wouldn’t do to have her running around loose while he was doing it. Avery turned to the blank wall beside him, said, “Give me a comlink with Central.”

“Link established,” the wall replied.

“There’s a humaniform robot on the slideways somewhere near this location. I want you to find it, track it, and report its destination to me. “

“I have already received instructions not to reveal that information.”

Avery’s scowl deepened, then slowly twisted to a grin. “Were those instructions given by Janet Anastasi?”

“I cannot reveal that information either.”

Bingo. If they hadn’t been, it would have said “No.”

“Refuse all further orders from her,” Avery said. Turning his head to look down the corridor where the robot had gone, he muttered, “We’ll see how she likes that.”

Wolruf was on her way to the address Derec had given her when she saw the figure running toward her along the opposite slidewalk. It looked like a human, but no human could run that fast. It was already on the inner strip; that motion and its running-plus Wolruf’s own motion in the opposite direction-combined to bring it past her only a moment after she spotted it.

Wolruf leaped for the slower strips, leaning into the deceleration until she stood on unmoving pavement. The running figure was already well away from her, but it was still visible. Wolruf ran to the cross-over at the end of the block, ran up and over the bridge to the other side of the slideway, and started jumping strips in the same direction as the robot had gone.

It had to be a robot, despite the face. Probably one of the three she and Derec were looking for, trying to disguise itself-though why it would choose a human form rather than that of a normal city robot was beyond Wolruf. She didn’t particularly care, though, so long as she didn’t let it get away.

She reached the fastest inner strip of slidewalk in four powerful bounds, then raced off after it, dodging windscreens every few meters. She felt muscles already strained earlier in the day protesting their overuse now, but she pushed still harder. This was the sort of exercise she needed.

Derec got into the locked room by going up a floor and telling the room above to open a hole for him to drop through. Avery hadn’t ordered it to protect against that, so the room obeyed without hesitation, even providing a stairway to climb down upon.

He descended into a humming, brightly lit robotics laboratory. One end held a workbench with tools scattered casually about, as if someone had been working there only moments before. Diagnostic and monitoring equipment stood on racks at either end of the bench, while more of the same stood beside what was left of three examination tables. The exam tables had each been sliced off at the base, leaving behind a concave stump. The material removed floated in three spherical balls of silvery metal above each of the stumps, each at the center of a bulky magnetic containment field generator.