The book opens with detective Elijah Baley on Earth, training with his son and others to overcome their socially ingrained agoraphobia, when he is told that the Spacer world of Aurora has requested him to investigate a crime: namely, that the mind of R. Jander Panell, a humaniform robot identical to R. Daneel Olivaw, has been destroyed by a mental block. The robot's inventor, Han Fastolfe, has admitted that he is the only person with the skill to have done this, but denies having done it. Fastolfe is also a prominent member of the Auroran political faction that favors Earth; wherefore, it is politically expedient that he be exonerated. En route to Aurora, Baley again is partnered with R. Daneel Olivaw, and introduced to R. Giskard Reventlov.
On Aurora, he interviews Gladia Delmarre (who first appeared in The Naked Sun ), R. Jander's former owner, and discovers that Gladia had a sexual relationship with Jander, to the point of considering him a husband. Baley later interviews Fastolfe's estranged daughter, Vasilia Fastolfe (alias "Vasilia Aliena"), who claims that her father would do anything necessary to advance psychohistory, including the incapacitation of Jander and Gladia's heartbreak. Following that, Baley interviews Santirix Gremionis, an Auroran who, with both Gladia and Vasilia, committed the Auroran taboo of offering himself repeatedly (sexually) after rejection. Gremionis denies involvement in the murder, and says he has reported Baley to the Chairman (the executive of the Auroran Government) for slander; but realizes, upon questioning, that Vasilia arranged his infatuation with Gladia.
Next, Baley interviews Kelden Amadiro, Fastolfe's chief political rival and head of the Robotics Institute, who explains the Institute's political motivations: that they wish to see Aurora alone colonize the Galaxy, by means of humaniform robots which at present only Fastolfe can build. On the way from the interview with Amadiro, Baley's airfoil (a personal hovercraft) is forced to stop. The air compressor has been sabotaged. Baley, suspecting Amadiro, orders Daneel and Giskard to flee. When several robots catch up with the car and question Baley, Baley tells them that he ordered Daneel back to the Robotics Institute, and they leave. Baley flees the car into the thunderstorm outside, where his agoraphobia renders him unconscious. He is recovered by Gladia and Giskard, and taken to Gladia's house. At an earlier-arranged meeting with the Chairman, Fastolfe, and Amadiro, Baley accuses Amadiro of sabotaging the car so that he could keep him, helpless, in the Institute, and thus have a legitimate reason to have Daneel there as well, unsupervised. As Baley states, without Fastolfe's cooperation, the only way to obtain knowledge about humaniform robots is to reverse engineer Daneel by thorough questioning, which would have allowed Amadiro to learn the details of his workings.
While logically consistent, Baley's unsupported accusation cannot stand against a formal denial by an Auroran as prominent and respected as Amadiro. However, Baley then confronts Amadiro with the revelation that Amadiro knew of the relationship between Gladia and Jander, and moreover, of her considering him her husband; something quite unthinkable for a native Auroran. Amadiro says he may have heard it from someone, but cannot remember whom.
Baley then states that only one Auroran could have told Amadiro about the relationship: Jander himself. Then, he gives the solution to the mystery: that in Gladia's absence, Amadiro questioned and tested Jander via trimensional viewing (telepresence). Daneel was part of Fastolfe's establishment, and thus well guarded, but Jander was at the house of the much less skilled Gladia, thus questioning him for reverse engineering purposes was much easier. Gremionis was encouraged to court Gladia because they tended to take long walks together, allowing Amadiro more time for his testing. The sabotage to the car was intended to capture Daneel and complete the analysis.
When Baley states that these experiments might have accidentally led to Jander's deactivation, Amadiro snaps and inadvertently admits he was working with Jander. As a result, he is forced to compromise with Fastolfe's policies; Amadiro agrees with Earth's right to share in the galactic colonization, while Fastolfe gives the Institute his data about humaniform robot design. Baley, however, confronts Giskard, who admits that Vasilia unknowingly gave him telepathic abilities during experiments. Using knowledge derived from Han Fastolfe's mind, Giskard shut down Jander, to thwart Amadiro's attempt to build humaniform robots. Giskard allows Baley to retain knowledge of his abilities, but prevents him from revealing the secret.