On Aurora, the central world of the cosmonites, a “robot killing” has taken place. Someone intentionally destroyed the brain of a humanoid robot. As Doctor Fastolfe believes, only he has enough knowledge on the entire planet to do something like that. But he didn’t. Fastolfe is the leader of a political movement that helps the Earthlings, and the Earth government really doesn’t benefit from losing his support—so it sends a person it has already tested. Bailey must unravel this delicate matter at any cost.