A catastrophic world war has left Earth radioactive and barely habitable. Animal life has nearly been wiped out. To encourage people to move to other planets, the U.N. supplies each emigrant with a lifelike android servant. Most people have taken the offer, but a few remain on Earth. The “regulars” can marry and travel freely. The “specials” (people who are damaged by radiation) are not allowed to reproduce or to leave Earth. Ownership of an animal is a status symbol. Some people own real ones, but others have to settle for lifelike fakes. Both regulars and specials participate in a ritual called fusion, which involves “empathy boxes” and a mysterious figure named Mercer. Through fusion, people share in Mercer’s physical sufferings and also transmit feelings to one another. Those who come to the ritual happy leave sadder, weighed down by others’ burdens. Those who enter the ritual sad have their spirits boosted by others’ happiness. The beliefs and moral teachings associated with this practice are called Mercerism.

Out on the colony planets, life is much less pleasant than advertised back on Earth. The android servants find their existence especially bleak. Some of them murder their owners and escape back to Earth, where the androids try to pass for human beings. Police departments employ bounty hunters to hunt these androids down and kill them. Before killing an android, however, a bounty hunter must use a psychological test to confirm that the target is an android. The test is believed to be reliable, but with each new model, androids are getting harder and harder to distinguish from real people. 

Rick Deckard is a bounty hunter attached to the San Francisco Police Department. One morning, he learns that a colleague was badly injured by an android. This android, plus five others on the colleague’s list, are now assigned to Rick. Rick looks forward to earning several bounties, and he starts thinking about which animal he will buy to surprise his wife. Before he can go after the androids, however, his boss orders him to visit the headquarters of Rosen Association, the manufacturer of the most realistic androids. Rick must confirm that the test to identify androids still works. 

At Rosen headquarters, Rick meets Rachael, supposedly the assistant and niece of the company president. Rick does not realize that Rachael and her uncle intend to derail Rick’s android-hunting. First, Rick is asked to use his test to decide whether Rachael is android or human. When Rachael tests as an android, the uncle persuades Rick that the test is wrong and therefore unreliable. This is a serious obstacle to any further android-hunting. Rick figures out, however, that Rachael truly is an android. Later, Rachael offers to help Rick hunt androids; being one herself, she should have useful insights into their thoughts and behavior. Rick refuses the offer. The androids he goes after use elaborate tricks to evade capture, but he persists. By the time he heads home from work, he has killed three androids and has used the bounty money to buy his wife a goat. He plans to resume the hunt the next day, but his boss calls and orders him to the location of the last three androids that same evening.

Rick changes his mind and asks Rachael for assistance. When Rick and Rachael are together, however, she seduces him. This is a tactic: nearly all other bounty hunters she slept with lost their zeal for android-hunting afterward. Rick, however, turns out to be one of the exceptions. He sends Rachael away and proceeds to his confrontation with the last three androids. They have been hiding out in the apartment of John Isidore, a special. One of the androids, Pris, is a duplicate of Rachael. Isidore is infatuated with her and in awe of android intelligence. This is the reason he is helping Pris and her two companions even though they treat him poorly. When Rick arrives, Mercer appears and warns him that Pris is lying in wait. Rick is caught off guard by Pris’s resemblance to Rachael, but he recovers and kills her. He then kills the other two androids more easily.

Rick’s hunt is over, but he feels empty and defeated. Mercerism, it was announced on TV last night, is an elaborate hoax. Rachael has taken revenge on him by killing the goat. Rick flies northward in his hovercar for hundreds of miles and sets the car down on a rocky hillside. Despondent and sleep-deprived, he experiences fusion with Mercer, even though he has no empathy box with him, and even though Mercer is supposedly not real. Rick spots a toad on the ground. Toads are listed as extinct, but against all odds Rick has stumbled on one in the wild. Excitedly, he brings the toad back to his wife. She discovers that it is only an electric toad replica, but she is grateful for the gesture. After Rick’s wife tucks him into bed for some much-needed sleep, she orders some supplies to care for the toad.