Do Androids Dream of Electric Sheep? : The Novel That Became Blade Runner

By 2021, companies have built incredibly realistic androids. Fearful of the havoc these artificial humans could wreak, the government bans them from Earth, but when androids don't want to be identified, they just blend in. Rick Deckard is an officially sanctioned bounty hunter whose job is to find rogue androids and "retire" them. But cornered, they tend to fight back, with deadly results.