 A policeman, Ross Sylibus, is assigned to a unit on a Martian colony, to find that women are being murdered by a psychotic named D anclaude. He is assigned a very unorthodox partner named Naomi Armitage, who seems to have links to the victims. To stir things up more, every victim is found to be an illegally made third-generation android, built to be almost perfect replications of humans. It becomes a race against time when the government attempts to cover up the existence of the  Third Types , and eliminate the only ones with the evidence. And even more importantly, why are the Thirds created to be so similar to humans, even to the extent of being indistinguishable from them on every level, mentally and biologically?