The Compass Tower of Robot City.
They were to find that Robot City was an intriguing place. The material of which it was composed was shaped like tiny Keys of Perihelion, and the city itself was undergoing constant change. Buildings would appear and move overnight. There was a constant blaze of activity by the millions of robots in the city, who claimed to be preparing this place for human inhabitants, though at the moment, the only humans here were Derec and Kate.
The city was in trouble. Nightly deluges raced through the streets, uncontrollable. Huge lightning storms daily menaced them. And there was a murdered human, a human named David who had looked exactly like Derec. Derec slowly realized that the city-as one robotic entity-was responding to what it considered to be a Third Law threat to its existence. The threat was David’s blood; more specifically, the microbes in it. The rainstorms were a byproduct of the city’s enormous and uncontrolled growth in response to that perceived threat. To save the city, he reprogrammed the central computer core to deactivate the city’s defenses.
At the same time, Kate made an effort to recover the Key to Perihelion, which she had hidden in the Compass Tower. It was gone. She and Derec were trapped here.
They found that the city robots had taken the original Key and were making duplicates of it. In the course of trying to steal one of the Keys, Derec and Kate began to develop a trust for each other.
Kate admitted to Derec that her real name was Ariel Welsh. She was the daughter of a wealthy Auroran patron of the sciences. Her mother had furnished one Dr. Avery the funds to design and build his pet project. Avery was an eccentric, argumentative genius who wanted to create on-going, self-sufficient cities to seed the stars for humankind. Avery, though, had disappeared. Robot City, Ariel guessed, was his original experiment, now running without Avery’s control. As for Ariel, she had been banished from Aurora because of her incurable disease, contracted from a Spacer. Given a ship and funds by her mother, she’d gone looking for a cure.
It was imperative for her to leave Robot City if she was going to live.
In the meantime, Robot City had acquired another human visitor: Jeff Leong, whose ship had exploded just outside the atmosphere. He was badly injured; to save him, the robots of Robot City turned him into a cyborg: a human brain encased in a robotic body. Insufficient knowledge of the bio-chemical structure of the brain led to Jeff’s slow insanity, though otherwise the surgery was a complete success.
Alpha and Wolruf had also made their way to the city via a modified Massey lifepod, big enough for only one human.
With Alpha and Wolruf’s help, Derec and Ariel were able to capture the increasingly violent and unstable cyborg. Using Derec’s body as a model, the medical technicians of Robot City were able to transplant Jeff’s brain back into his own newly healed body. However, he remained ill and largely out of his senses.
Alpha, during the capture of Jeff, had received instructions from the cellular material in his flexible arm ordering the robot to change its name to Mandelbrot. Derec suspected that the arm, from an Avery-style robot, might well have also sent a signal to Avery to return to Robot City.
A choice had to be made: let Ariel take the lifepod and escape, or send Jeff back. Ariel insisted that Jeff must be the one to go.
Robot City continued its fascinating evolution. Not long after Jeff’s departure, the behavior of the robots began to show definitely odd tendencies. Circuit Breaker appeared: a building like two four-sided pyramids stuck together at their bases and balanced on one point. The building, the first work of creative art built by a robot, reflected ever-changing colors as it rotated. Three robots, calling themselves the Three Cracked Cheeks, formed a Dixieland jazz band. All this came about as an effort by the city to formulate what it called the Laws of Humanics-corollaries to the Three Laws of Robotics. The Laws of Humanics were supposed to govern-or at least explain-the actions of human beings as the Three Laws of Robotics governed those of positronic intelligence.
The most serious and unusual event in all the strangeness was that a robot was murdered by another robot. Lucius, the creator of Circuit Breaker, was found with all its positronic circuitry deliberately destroyed, so that the brain could never be reconstructed. It seemed a deliberate attempt to stifle the advances made by the Avery robots.
In the midst of this, Avery himself returned to the city, and Derec, Ariel, Wolruf, and Mandelbrot quickly discovered that the doctor was a dangerous megalomaniac. All that mattered to Avery was his work; he could not have cared less about Ariel’s illness or the plight of the others. All that mattered to him was Robot City. He had stationed Hunter-Seeker robots around the area to take all of them prisoner until he could analyze all that had happened here-in whatever way was most convenient to him.
They were taken prisoner, and Derec, unknowingly, was given a dose of chemfets: miniature replicas of the city material that took residence in his bloodstream.
Escaping at last, Derec, Ariel, Wolruf, and Mandelbrot left Robot City on Dr. Avery’s ship. There, in a hidden compartment, they found a Key to Perihelion.
It was obvious that Avery anticipated their escape, for the ship was sabotaged. Without the ability to home in on the navigational beacons, they could not program the jumps through hyperspace. Ariel had also taken a definite turn for the worse. Derec decided that he and Ariel must use the Key to Perihelion to try to get help for her. Wolruf and Mandelbrot would remain with the ship and try to complete repairs or attract help from another ship.
Derec activated the Key, and he and Ariel found themselves in an apartment on Earth. They found Earth society paranoid and isolated, with extremely xenophobic attitudes toward Spacers. However, Ariel was getting progressively weaker, and Derec in desperation took her to a local hospital. If Earth was backward in some ways, it seemed that its medical facilities were better than Aurora’s. They recognized her disease-amnemonic plague-and cured her.
Unfortunately, the chemfets in Derec’s body were asserting their presence, and he was rapidly getting weaker himself. With the help of R. David, an Earth robot, they stole a ship from an Earth spaceport and headed out to rescue Wolruf and Mandelbrot.
Another spaceship followed them: Aranimas, who had tracked the bursts of Key static to Earth. In a tense battle, Derec and Ariel, with Mandelbrot and Wolruf, managed to destroy Aranimas’s ship at great cost to their own vessels. They had only one option left to them with Derec growing weaker: use the Key to jump back to Robot City.
They emerged from the Compass Tower into Avery’s vacant office, intending to force the doctor into helping Derec. To find him, Wolruf and Mandelbrot went into the city, while Derec and Ariel began searching the tunnels underneath the tower.
Mandelbrot and Wolruf found that the robots were all following the orders of what they called the Migration Program. They were leaving the first Robot City and seeking new worlds on which to build. And when they returned to Compass Tower, they found that Hunter-Seeker robots were searching for Derec and Ariel, who had fled.
Above the planet, a small spacecraft arrived, carrying Jeff Leong. Back to normal, he was returning to rescue the others. Meeting with Derec and company, he was determined to help them find Dr. Avery.
It was actually Dr. Avery who found them, the Hunter-Seeker robots capturing the company one by one. The Doctor revealed that Derec was actually David Avery, Dr. Avery’s son, and that the chemfets in his body would one day allow him to control every Avery robot in existence. Derec would become Robot City.