He turned away from the screen and spoke directly to them. “So here’s what happened: Building movement is essentially random, subject to supervisory override if the random number generator comes up with a ridiculous configuration. It doesn’t happen often, about once a day, on the average. So without a supervisor to veto it, today’s ridiculous building gets built. It turns out to be ridiculously tall. But the main power station doesn’t have a supervisory order to generate more power for it, so when it starts to pull excessive current to lift all that mass, it trips the breaker. Power goes out. The original emergency programming has been blocked-twice, I point out with injured dignity-so without a supervisor’s order, the auxiliary stations don’t go on line. The building is unstable without power to hold it up, so it falls over. On the power station.”

“Oh,” Derec said. One word can be expressive under the right circumstances.

Ariel said, “So we messed it up, that’s what you’re saying? It’s our fault?”

Avery shook his head. “It’s everyone’s fault. Mine for not writing the original program to filter out the bad input before it reached the supervisors, yours for bypassing the emergency programming, the Ceremyons’ for bypassing your bypass, the experimental robots for distracting the supervisors-take your pick. We’ re all in this together.”

“Even me?” Wolruf asked. The bandage across her forehead made her look a little like a pirate in a bad movie, and her toothy grin only added to the illusion.

“Even you. And yes, I’ve included you in the city robots’ new definition of human. Basically I put them back to the old definition of anyone genetically similar to us, plus you. And I strengthened their devotion to duty as far as I can push it. That ought to keep them from listening to subversive arguments.”

It seemed to do the trick, all right, but their problems were far from over. The robot rebellion might have been quelled, but robots weren’t this planet’s only inhabitants.

The next morning the four “humans” were examining the wreckage when a black speck dropped down out of the sky, grew rapidly in size until it became visibly winged, and swooped in to stall to a stop just in front of them. It had the same shape as the three robots had when they returned from their discussion with the Ceremyons, but it was easy to tell that this was the real thing. The alien folded its wings and took a step closer until it stood before Ariel.

Ariel had been the one to initiate communication with the aliens before, and they had come to regard her as a leader among humans.

“You are Ariel,” the one before her said in a high-pitched voice. “I am Sarco. We have met.”

It was hard to see detail in the alien’s body. It gained its nourishment from solar radiation, so it was an almost perfect black, reflecting not even the slightest amount of light back into its environment. The effect was like that of talking to a shadow, or to an eclipse. Only the white hook, with which it tethered itself for the night, and its two deep red eyes broke the darkness.

As far as Derec knew, Avery had never seen an alien before, but he played it cool. He studied the creature before them silently while Ariel replied, “Hello, Sarco. Good to see you again.”

“I wish I could say the same, but unfortunately, I come with a complaint.”

The alien’s speech had improved considerably since Derec had last heard it. Before, it had sounded a little like someone with an Earth accent and a cold on top of it, but now it just sounded like it had a cold. It had evidently been practicing.

Derec could guess what the alien had come to complain about. Their society valued peace and quiet and maintaining the status quo; when he had dealt with them before, they had been ready to isolate the entire city under a force dome simply because they didn’t like the heat it radiated. Now…

“You don’t like buildings falling over in the night?” he asked facetiously.

“You are Derec. I do not.”

Avery cleared his throat. “Neither do we.”

Sarco turned his head, a motion evident only by the shifting position of the eyes and the hook. “We have not met.”

“I am Doctor Avery. I designed the robots that built this city.”

“I see. They have caused us considerable trouble. You neglected to include proper feedback mechanisms to limit their spread. We had to do that for you.”

Avery hadn’t expected such a direct accusation, but he took it gracefully. “I apologize. Causing you trouble wasn’t my intention. When I sent them out, I didn’t know you were here.”

“Now you do. Will you remove them and their city?”

Avery frowned. “That would be difficult.”

“But not impossible.”

“No, not impossible. But definitely difficult, and probably unnecessary. Since the planet is already inhabited, my purpose for the robots can’t be realized here, but I’m sure we can adapt them to be useful for you.”

“We already attempted that. We need neither servants nor farmers.”

“Well, what do you need?”

“We need nothing.”

Avery snorted. “That’s a little hard to believe. I’m offering you a whole city full of robots. Maybe you don’t realize it, because their programming so far hasn’t made much use of the capability, but the robots can change their shapes as readily as the city can. I can turn them into anything you like, and the city as well.”

Sarco rustled his wings. “We have no need of a city full of robots, no matter what their shapes.”

Avery shrugged. “Think about it. Derec tells me you guys are pretty bright. You should be able to come up with something you can use them for.”

A tiny jet of flame appeared in the blackness below the alien’s eyes. It was a sign of irritation, Derec knew. The flame went out, and Sarco said, “I will take the matter up in council. Perhaps we can think of something, so you will be spared the inconvenience of removing them.” He stepped back, spread his wings, and with a powerful thrust leaped into the sky.

Avery watched him rise until he was out of sight, then shook his head and began walking along the collapsed building again. “Touchy, aren’t they?” he asked of no one in particular.

The three renegade robots were nowhere to be found. They had stopped bothering the city robots when they realized that Avery’s new programming was too tight for them to influence, but from that point on they effectively disappeared from sight. All of the city robots were under strict instructions to report the others if they were spotted, and to detain them if possible, but nothing came of it.

Derec tried the comlink, but was not surprised to receive no answer.

Within the space of the afternoon, the fallen building and its wreckage was nearly cleaned up. What city material that couldn’t be immediately returned to the general inventory by simply instructing it to melt back into the street was hauled away to the fabrication site to be reprocessed, and the robots who had been damaged were repaired or replaced in the same way. By evening things were almost back to normal, right down to the medical robot who called the apartment just after dinner.

It was time for Ariel’s checkup. She and Derec walked the short distance from the apartment to the rebuilt hospital alone. Wolruf sensed that they didn’t need company, and Avery was already there in the hospital, working on another rat. They didn’t talk. There was nothing to say. Either the embryo was developing normally again or it wasn’t, and nothing they could say now would change it.

All four medical robots waited for them in the hospital. Derec held Ariel’s hand while they set up their equipment around her, made their measurements, and studied the results. He knew from their silence what the outcome was long before they worked up the nerve to tell him.