“Hey, Euler!” Derec repeated. “Why isn’t he answering? What’s wrong with him?”

Euler walked right up in front of them and stopped. The little function robot whirred and rolled away, apparently in response to a comlink order.

“Greetings, Derec. You are not allowed here. Come with me.” Euler stepped aside to let them go first.

“What kind of a welcome is that?” Derec demanded, walking forward reluctantly. “Euler, it’s us. We’re back. And we need help and information.”

“I recognize you, Derec and Ariel.” The robot was walking just behind them both.

Derec had the uneasy feeling that they were being guarded rather than accompanied in a friendly fashion. “You used to call me Friend Derec,” he pointed out.

“We are conducting urgent and important business,” said Euler. “You are acquainted with Robot City and you know you will be safe here. You must leave the Compass Tower.”

“I told you we need help!” Derec shouted angrily. “The First Law! Have you forgotten all about it-”

Ariel tugged hard on his sleeve, slowing him down. He shook her off, turning to stop and face Euler eye to eye.

“No,” Ariel insisted. “Don’t give anything away. Something’s gone wrong.”

Derec froze in his angry posture, glaring at the impassive face of the Supervisor. He hesitated, absorbing the unexpected behavior of Euler. She was right.

“What’s happened?” Ariel asked Euler. “Why are you acting different now?”

“You are not allowed in the Compass Tower.”

“Wait a minute,” said Derec. “What about your study of the Laws of Humanics? Remember those? You need humans for that.”

“Please continue forward. You will be removed by unharmful force if necessary.”

“Ha! ‘Unharmful force’? You don’t know how fragile we are, do you?” Derec laughed derisively.

“What’s happened since we were here last?” Ariel asked. “Have you changed your plans for the city?”

“Come with me.” Euler reached out with each pincer and took their arms.

Even the gentle pressure caused a snapping of adhesions in Derec’s arm. He winced in surprise, though the feeling was partly one of relief. The pincer immediately withdrew.

“You hurt me!” Derec shouted. “Ariel, come on!” He grabbed her arm and started to run.

His legs burned painfully and his back felt oddly stiff as he tried to hurry down the hallway. She was already ahead of him now and pulling him, rather than the reverse. Behind them, Euler was hesitating, his decision-making slowed by Derec’s accusation.

Ariel pulled Derec around a corner and down another hallway. “They’ve been reprogrammed,” Derec called to her, panting. “They must have been. If the robots had evolved new priorities themselves, they would still have the same personalities.”

“Shut up and come on!” She turned another corner.

Derec stumbled after her, forcing his legs to stretch out. “Look for an elevator!”

They skidded around another corner, trying to gain traction on the clean, polished floor. Her grip had slid to his hand, and their arms were fully outstretched as she pulled him along after her. She turned another corner, continuing a zigzag pattern.

“Do you know where you ‘re going?” Derec asked, as quietly as he could.

Ariel slowed to a halt at another intersection of hallways. No pursuit was evident yet, but in a building this size, the Supervisors could certainly marshall a large number of function robots to detect their presence. Some humanoid robots would undoubtedly be around to join the chase, also.

“No, I don’t know where I’m going,” she said.

Derec looked behind them and down the four halls that met where they were standing. “Where is everybody?” He gritted his teeth against the pains shooting through his legs and his back.

“Come on.” Ariel started again, then noticed he was still looking down the other hallways. She leaned back to grab his hand and pull him after her.

They turned several more corners, always looking for doorways or main hallways.

“There!” Ariel shouted, as they rounded one corner. “Isn’t that an elevator?”

“Worth a try,” he gasped, wheezing as his chest heaved for air. “Hit the button. I think we’re in real trouble.”

They waited anxiously, looking behind them as they waited. At last the door opened, and again the elevator was empty. They got inside and Ariel hit the bottom button.

Derec fell back against the wall for support and closed his eyes. “I hope nobody’s waiting for us when the door opens.”

“What did you mean, we’re in real trouble?”

“Two things. The way Euler acted, I think Avery reprogrammed all the Supervisors while we were gone. That means the whole city is operating under different rules. I’m also guessing that as soon as our presence was reported in Euler’s positronic brain, the central computer reported right to Avery, wherever he is.”

“Then why isn’t anyone chasing us?”

“I’m afraid…he’s ordered Hunter robots after us. And the others are simply staying at their regular duties.”

The elevator door opened into dim light. No one was waiting for them, however. Derec stepped out first, looking around.

They appeared to be in a small tunnel stop. In most of the others, the multiple tracks were visible from the loading area. Here, a wall isolated the siding, keeping it out of the sight of travelers passing on the main trunk.

Derec edged toward the siding and looked around. He could feel the rush of air moving past him from one side to the other as it blew in from the main tunnel. Ariel followed him.

“I pushed the ‘wait’ button,” she said. “They won’t be able to call this elevator back up.”

He nodded approval. “Come on.”

They crowded into the single platform booth waiting on the siding. He started to punch a code into the console, then hesitated.

“What’s wrong? We have to get away from here as fast as we can.” She tugged on his arm.

He entered a code for a tunnel stop just a short distance away and the booth started to move. “The tunnel computer is a branch of the central computer. As soon as someone asks, it will report our destination.”

“What?”

“That’s right.” He nodded grimly. “We have to get away from here and get out quick. If we ride too long, we’ll have a welcoming committee by the time we stop.”

The transparent booth followed the siding around a curve and onto one of the parallel tracks in the main tunnel. Derec looked around anxiously at the stolid robots riding nearby booths, but none showed any interest in them. On the other hand, the robots presented their customary expressionless aspects while riding the booths, and if one was scared enough -as Derec was now-they seemed stern.

A paranoid might easily imagine that they were secret escorts, not incidental travelers.

He shook his head angrily. That line of thought would make him as crazy as Avery.

Suddenly the booth slowed and swung into another siding. This was an ordinary stop, with a loading area fully visible from the main tunnel. That stop under the Compass Tower was the only disguised one Derec had ever seen.

“Nobody’s waiting for us,” said Ariel as the booth came to its carefully calculated stop. She stepped out onto the empty loading platform.

He came out behind her. “If Hunter robots are on the way, they may just be getting the coordinates now. They can pick up our trail here, though, without going to the Compass Tower at all. I-hey!”

“Derec, what is it now?” She wailed.

He whirled and leaned back into the platform booth. After a quick glance down the way they had come, he entered a series of further coordinates, punching codes as fast as he could remember them.

“Derec, let’s go.” She looked down the main tunnel anxiously herself. “What are you doing?”