This sci-fi mystery takes place in the distant future when the Earth is vastly overcrowded and the entire population lives underground and has severe phobias about going outside.
When the story opens a humanoid robot has been "killed" on the planet Aurora which was colonized by Earth people long ago. A famous roboticist - the only one in the galaxy who knows how to create humanoid robots - is accused of the crime. The detective Elijah Baley, an Earth-man, is called in to investigate with his robot partner. Elijah's job is made doubly difficult because most Aurorans despise Earth people, considering them to be infectious and vastly inferior to themselves.
The case is very important because its solution may determine whether space is further colonized solely by humanoid robots and Aurorans or whether Earth people will be allowed to participate.
Some interesting twists and turns lead to a satisfying surprise ending.