It was probably his imagination. The Silversides, Ariel, all his responsibilities were making it work overtime. He was just plain exhausted, frustrated-that was probably the answer. He would have to make himself human again, rebuild his own personality the way the figures below rebuilt the city.

Lately Derec had had the sense that since his awakening in an amnesiac state, he had become a robot himself. He was increasingly concerned with his duties (one crisis after another, it seemed) and, like the robots below, rushing to goals that were usually shadowy and mysterious.

Sometimes he felt he was divided inside between the human and robot sides of his personality. Certainly, because of the chemfets, he was at least part robot. At times the human side ruled his life and emotions; at other times the robot part took over. He was human at the height of a crisis, when a battle had to be fought or a decision made; human when he was with Ariel, at least in the loving and tender times, or even the angry ones; human when he had to instruct and guide the robots or intellectually confront Avery. On the other hand, in between these active human periods, there were times when he allowed the robot inside him to take over. The robot was in charge when he had to do the dirty work, the menial activities that occupied so much of his duties. He was also robot when he felt nothing but an emptiness inside toward Ariel or Wolruf or Mandelbrot, the trio who meant so much to him now. There were times when he suddenly realized that time had passed and he had only the vaguest idea of what he had done during it, and in his mind that became the robot’s time rather than the human’s. He wondered if a robot, along some pathway of his positronic brain, was ever conscious of everyday routine.

After landing, Derec was surprised to find the spaceport deserted. Usually a few maintenance robots were in evidence, searching for rarely found trash, shining up already shiny surfaces. The spaceport seemed to Derec like an enormous white elephant, an area that functioned only when he or Ariel used it. Of course, much of Robot City was like this-structures designed for thousands or even millions of human immigrants, magnificent living quarters for people-to-come, commercial setups for invisible shoppers, workplaces used now only by programmed robots who mainly made tests of equipment.

As they passed through the deserted terminal, Adam and Eve looked about, their heads snapping from side to side as they tried to absorb all the new information. To Derec it looked as if the two chameleonic robots were searching for someone or something to copy. He smiled. There’d be no new beings to change into in Robot City. The robots they’d encounter were so much like ones they’d already seen, they would, as Wolruf predicted, grow bored and become more malleable to human manipulation. Then perhaps Derec could straighten the two little buggers out.

“Shouldn’t someone be welcoming us or something?” Ariel asked.

“I’m not sure,” Derec answered. “I’m not up on spaceport protocol. It just seems that we should be seeing a few robots behind a few counters or something.”

Outside the terminal, at the proper station, they found a floater, so called because it went down Robot City roadways without actually touching pavement. It was a two-seater, so Derec told Wolruf and Mandelbrot to locate a larger vehicle and follow him and Ariel into the city. “Keep a lookout for anything that looks out of sync,” he said to them. “We’ll rendezvous at the Compass Tower and compare notes.”

On the ride down the long access road to the city, Ariel said, “Now that you’re here, what do you feel, Derec?”

“I still can’t make any sense out of the chemfets. But I don’t know what’s wrong. Something has changed here, but I can’t see it yet.”

“If you don’t see something, how do you know it exists?”

“That sounds faintly philosophical.”

“My habit. Sorry.”

The floater was small, so small that their shoulders, hips, and legs were pressed together. Normally he liked being this close to her, but today there was a stiffness in the way she held herself. It made him uncomfortable to be touching her at all.

He smiled at her. She stubbornly refused to smile back. Although she tried to look relaxed, her tension was apparent in her eyes.

Touching the bar that controlled the vehicle, Derec brought it to a stop at the first block of buildings after they crossed into the city proper. He got out before the floater had settled down onto the pavement.

“Where’re you going?” Ariel asked, as she, too, squeezed out of the vehicle.

“Just a look around.”

He approached the side of a cube-shaped building and stared at it. “Look at this.”

Standing beside him, she tried to see what he saw.

“What is it?”

“That seam there.” She had to squint to see it. “The city is assembled from five-meter-square slabs that come out of an extruder in a sort of ribbon. The material forms and reforms, following some sort of predetermined programming. It becomes windows, walls, rooms, entire storeys of buildings, structuring itself. It’s done so flawlessly there should be no seams, cracks, openings, except where architecturally logical. This seam isn’t logical.”

Looking closer, she could see that there was indeed a tiny separation. Only a very thin coin could get through it, but it was certainly a flaw.

He strode away from her, running his hand along the wall and around a corner. When he was out of sight, she heard him yelp. She ran around the corner to find him staring down at his little finger.

“Look,” he said, holding out the finger to her. There was a tiny cut at its tip and a minuscule drop of blood had oozed out. She was always surprised by how much darker than hers his blood was.

“What happened?”

“The damn thing cut me, that sliver there.”

“Sliver? But that’s impossible. You once told me the building material is programmed with the First Law. It can’t allow you to get hurt, especially on it.”

“That’s right. By all rights, I shouldn’t be bleeding. Well, take a gander.”

The sliver was even more minuscule than the split seam, but it was there, all right. A tiny bit of red at its tip made it slightly more visible.

“What’s happened?”

Derec did not stand around long enough to respond to her question. He was several steps farther on, his eyes nervously inspecting another building, a small sloping structure that thrust upward into the sky, ending in a spire.

“Look up there!” he cried.

He meant the spire. As she peered at it, she realized that there was something just slightly out of kilter about it.

“It’s tilted a bit,” she said.

“Right,” he said. There was an offensive tone in his voice, as if he were condemning her for verifying the obvious.

“No Supervisor robot would allow such a deviation from the norm.”

“I don’t know. I seem to remember something I read about Earth and a leaning tower there. It was quite a tourist attraction.”

“Well, I’ll refer your observation to our Tourist Board.”

“Don’t be sarcastic. I’m trying to help.”

Again he didn’t respond. He was now running, eager to examine another building. Ariel clapped her hands twice as a signal to the floater. The pair of claps made the vehicle rise from the ground and follow her as she walked to Derec.

He stood in front of the building’s entrance and stared at it.

“Anything wrong with this one?” she asked.

“Nothing I can see. I’m sorry I snapped at you. I just feel at-”

“Forget it, buddy. I ragged you pretty hard back on Aranimas’s ship when we first met. We’ll just consider your present mood a paying back.”

“Thanks.”

As his eyes scanned the wall in front of him, his concentration was broken by a loud thumping sound.

“What was that?” Ariel asked.