Anton Saraste lives in a world where robots do the dirty work and all of the humans are genetically engineered to one degree or another. Anton was designed for intelligence, but his parents died young, leaving him without support and encouragement. Rather than abandoning his younger sister, Jane, Anton started working to support her musical ambitions. Jane and three of her friends form the Screaming Genes, a rock band on a slow ascent through the local music scene. Anton hates robots and people who didn't use their opportunities; he loves quiet things, mystery novels and reading about the history of science. His life is boring: he's a bouncer at their favorite club, a tame and civilized place, and he works part-time as an accountant. One night changes all of that.

Robots in Anton's society know their place. They've been programmed with MAPs (Modified Asimov Programming) to keep them from harming humans or acting on their own behalf. But one night at the club, a robot under the influence of randomized electrical pulses punches Anton's friend Bart. While the others help Bart to the hospital, Anton pursues the robot. He loses the robot in a crowded party, where he meets Moira, a lovely and friendly programmer who invites him back to her apartment to take a look at the randomizer the robot was using. Moira is distracting enough that Anton decides the randomizer can wait until morning. But when morning comes, the randomizer is gone.

Anton soon finds out that Moira is part of an underground movement to stop the use of MAPs. The people she works with believe that robots need to be free to defend themselves and determine their lives. Anton grows to understand that the sullen, difficult robots he deals with daily are slaves, and that free robots have the capacity to be brilliant, quirky, fascinating, flawed, and above all human. He gets involved with Moira and with the underground movement, meeting all of Moira's mentors, including Father Brian, the Catholic priest who's more or less in charge.

Just as Anton is beginning to adjust to his new life dating Moira and working with the robot freedom movement, his past smacks him in the face with the reappearance of his ex-girlfriend, Sylvie. Anton never understood why Sylvie left him. He certainly can't fathom why she's requested that he have power over her medical decisions eight years later, or why she attempted to kill herself, or what her bizarre method means.

When all the attempts to save Sylvie's life fail, Anton is plunged into a depression. His old friends can barely touch him in his grief. Only Moira and her movement show him that he can still do something that matters, and that he can move on with his life. The group especially needs his connection with John Burnham, the father of one of the members of Janie's band. Burnham is one of the executives for the robot manufacturers, and he has a vested interest in keeping the robots as trade-able commodities. He and his colleagues become interested in Anton when they find out about Anton's reaction to Bart's accident with the robot. They think they can use him -- even to kill for them -- if only the reward is high enough.

When Father Brian is killed in an attempt to implicate the free robots, Anton knows he has to find out what the Burnhams are up to. They want him to kill more of the ringleaders of the movement -- that is, the ones they know about. Anton warns the others of the danger, and of the upcoming plans to discredit free robots for years to come.

Burnham's son, Steve, finds out that his band mates are up to something, and he follows them to find out what. Anton insists that they can't trust Steve and tries to keep him from finding out the details of what they're doing. But in the end, Steve rejects his parents' organization and turns to the others to help them with the robot rights organization. Anton grudgingly accepts him into the group, but always keeps his eyes open for signs of treachery.

Gradually, Anton and his friends find themselves in more and more danger. The Burnhams ask Anton to kill Ophelia, and he helps her to flee for her life. They get the police to arrest her. Someone he doesn't recognize tries to kill Anton. And he contacts Sylvie's old hero, an independent investigative journalist, with the details of her death, hoping that the reporter can help him track down what was really going on.

The band gets notice that an agent will be coming to hear them play, on the very evening that the Burnhams are planning a big staged raid to discredit independent robots. They must move from playing their hearts out to fighting for their lives and reputations in a matter of hours -- and Janie is kidnapped in the thick of it. When the dust settles, the Burnhams have been defeated for the time being, but Janie is still gone. The attempts on Anton's life turn out to come from Sylvie's killers, the people who genetically engineered her to be their pawn and tossed her aside when they couldn't use her any more. The journalist, the band members, and Anton rescue Janie by trading information for her, but their robot friends demonstrate why, exactly, it's a bad idea to upset independent, free-thinking robots. The band gets signed for a tour, bringing with them a portable laboratory to distribute the pseudo-randomized cubes they use to deprogram the robots, and allow them to reprogram themselves. Moira and Anton stay home to do further work on the robots' problems -- and to get to know each other better.