By 2021, the World War has killed millions, driving entire species into extinction and sending mankind off-planet. Those who remain covet any living creature, and for people who can't afford one, companies build incredibly realistic simulacra: horses, birds, cats, sheep. They've even built humans. Immigrants to Mars receive androids so sophisticated they are indistinguishable from true men or women. Fearful of the havoc these artificial humans can wreak, the government bans them from Earth. Driven into hiding, unauthorized androids live among human beings, undetected.