A merry little surge of electricity piped by automatic alarm from the mood organ beside his bed awakened Rick Deckard. Surprised — it always surprised him to find himself awake without prior notice — he rose from the bed, stood up in his multicolored pajamas, and stretched. Now, in her bed, his wife Iran opened her gray, unmerry eyes, blinked, then groaned and shut her eyes again.
[incipit]
Rick Deckard is a bounty hunter, that is a police officer whose job is to find androids arrived illegally on Earth and "retire" them, which is an euphemism for killing them.
We're in San Francisco, in a world devastated by World War III, still threatened by radioactive dust in the air, an hostile and almost uninhabited world. With the "special" (human beings seriously damaged by dust) who is not allowed to emigrate, stands still a handful of normal human beings who refuses to leave for the Martian colonies, despite the attractive government incentives.
And then there are the androids, who even knowing they'll face certain death, they flee to Earth, to pursue what has always been their only dream: being human.