In 2046, the overpopulation of Earth has led to the colonization of Mars—with the aid of the "first type" androids, men were able to begin terraforming the unfriendly environment of Mars and build the city Saint Lowell. Some time after the start of colonization, the city is completed and inhabited by great numbers of people and "Second type" robots, much improved versions of the "First types". Ross Sylibus, a middle-aged policeman from Chicago, flies to Saint Lowell using a space shuttle. Sylibus asked to be transferred to the Martian Police Department to escape from his past and haunting memories of his previous partner being killed by a robot. At the Saint Lowell's space port he is to meet his new partner—a young woman named Naomi Armitage.
