“It’s still a very big city,” Ariel said doubtfully. Suddenly, she gasped. “That’s it, Derec. What are they going to eat?”

“Well-I guess they’ll get a chemical processor from the robots…”

“But will they know that? Will they know to ask? Besides, the robots wanted you to solve a mystery for them, so we had special consideration.”

“Maybe, but if the robots learn of the problem, the First Law will make them help out.” He was stung by the fact that he hadn’t thought of this himself. “Yeah, this must be the only city to be found anywhere that doesn’t have a single restaurant or anything like that.”

“This is our first real lead,” said Ariel with a new excitement. “Once we get back to the tunnel system, let’s split up. I’ll follow up on our latest sighting and see if I can find a food source around there.”

“Why? I thought you didn’t consider that lead worth much.”

“Oh, Derec, stop griping. You need to get back on the computer and see if you can locate food sources through it. This way we can cover two leads at once, that’s all.”

“Well, I can’t argue with that. Come to think of it, if they haven’t found any food, they could be in bad shape by now. We don’t want them dying on us.” He waved for her to follow him, pressed by a new sense of urgency.

“We can’t walk all the way to the tunnel stop,” she said, but she was smiling. “It’s good to see the old enthusiasm back.”

They actually walked some distance before a vehicle came by to give them a ride, but the walk paid off. The vehicle had departed from somewhere within the construction perimeter and would not have passed them out there. As Ariel had suggested, they split up in the tunnel system. He returned home to their computer console, while she went on to the site that Class 9 Vehicle 214 had reported.

Derec sat down at the console, glad to have another approach to use; but he hadn’t forgotten that this report had been lost somewhere in the system. He started by calling up a list of stores that were edible to humans. The only inventory was in the tank of their chemical processor, according to the screen. So either the visitors were getting hungry, or they had a food source not recorded this way.

Next, he called up other materials that had been converted to edible form. Again, everything was accounted for. He asked if another chemical processor had been made or requested. Nothing like that had been recorded.

As far as Derec knew, Robot City did not have any animal life that could be caught and eaten, even by the most desperate humans. Perhaps a very talented human could build a chemical processor without the help of the robots, but it would still require parts. Nor could it produce any food without raw materials of some kind.

On the assumption that the visitors had landed outside the city and entered the perimeter where he and Ariel had first gone, he narrowed the focus of his requests and asked again if any robots in that area had sighted the strangers. Nothing turned up that way. He got the same result when looking for a record of their landing.

The only certainty Derec had was that the computer was unreliable. The answers about the chemical processor and the foodstuffs might be accurate, but the visitors were here, and that meant they had landed somewhere on the planet in a spacecraft that could, in all probability, lift off again. There had to be some way to track them.

He couldn’t think of anything. With a sigh, he got up and paced idly around the small room. So far, the computer hadn’t helped any this time; he wished he had gone with Ariel.

He doubted she was in much danger, especially if the visitors were a robot and a small child. Besides, he knew she could take care of herself pretty well. His attitude toward her had changed, though, ever since he had learned of the seriousness of her illness. She didn’t seem quite so intimidating any more, though she was still older and more self-assured than he was. Ever since the day she had told him of the severity of her disease, and had cried in his arms, he had felt a growing protectiveness toward her.

She seemed to be okay now, though. He figured she might just laugh if he tried to tell her how he felt.

His jaw muscles tightened with the determination to prove what he could do with the computer. He sat down again and started calling up everything he could think of regarding space: records of astronomical observations, spacecraft landings, liftoffs, fly-bys…what else?

The computer gave him nothing on recent soft landings of spacecraft, or crashes. Nor had there been any reported sightings of landed spacecraft. Astronomical observations had not recorded any craft in orbit, either. He had to assume that either the sensors had failed in some way, or that the information was simply lost in the computer.

Food, he thought. The visitors required nutrition. That was still the best lead he had, if he could only think of a way to exploit it.

Ariel walked out of the tunnel stop and located the coordinates of the last sighting of the visitors without any trouble. Her only problem was what to do next. She was in the middle of the city, standing still as a moderately heavy traffic of robots passed her, either on slidewalks or in vehicles.

“Well, what would I do for food here?” she asked herself out loud. “Ask around, I suppose.”

As always, the robots were moving with their single-minded deliberation. The bland buildings reflected that attitude in their austere efficiency of design. No stranger, she reflected, would expect to find food in this neighborhood.

She stopped the nearest robot passing, by calling out, “I am a human who needs questions answered. Stop.”

The robot stopped.

“Have you seen a robot traveling with a human child?”

“No.”

“Do you know where I might find food?”

“Food. This is the energy source for humans, is it not?”

“Yes. It must be provided in a certain chemical form.”

“I am not familiar with it. I do not know where to locate any. Are you in urgent need of energy?”

“I’m not,” said Ariel, “but I think a small human in the company of a certain robot probably is. Almost definitely. I need to find them before the child starves. That is, runs out of energy.”

“This constitutes a First Law requirement, then. I will help you search for them.”

“Identify.” Ariel suddenly realized that this argument could be used to harness every robot in Robot City.

“I am Courier Foreman 189.”

“You supervise couriers? What do they do?”

“Couriers are function robots that carry small items to specific locations. Objects and distance vary.”

“All right. Listen. You don’t have to interrupt your work at all. Just spread the word to other humanoid robots as you go about your duties that a First Law problem requires their aid in locating a human child in the company of a robot, and also another human wandering around by himself.”

“Understood.”

“And tell them not to include me-I’m Ariel Welsh-or Derec.”

“Understood. I will contact other robots through my comlink.”

“Good! I have to tell Derec about this right away.” Ariel turned and ran for the tunnel stop.