Invasion of the Body Snatchers is a 1956 American science-fiction horror film produced by Walter Wanger, directed by Don Siegel, and starring Kevin McCarthy and Dana Wynter. The black-and-white film, shot in Superscope, was partially done in a film noir style. Daniel Mainwaring adapted the screenplay from Jack Finney's 1954 science-fiction novel The Body Snatchers. The film was released by Allied Artists Pictures as a double feature with the British science fiction film The Atomic Man (and in some markets with Indestructible Man).
The film's storyline concerns an extraterrestrial invasion that begins in the fictional California town of Santa Mira. Alien plant spores have fallen from space and grown into large seed pods, each one capable of producing a visually identical replacement copy of a human. As each pod reaches full development, it assimilates the physical traits, memories, and personalities of each sleeping person placed near it; these duplicates, however, are devoid of all human emotion. Little by little, a local doctor uncovers this "quiet" invasion and attempts to stop it.
The slang expression "pod people" that arose in late 20th-century U.S. culture refers to the emotionless duplicates seen in the film. Invasion of the Body Snatchers was selected in 1994 for preservation in the United States National Film Registry by the Library of Congress for being "culturally, historically, or aesthetically significant."
A psychiatrist, Dr. Hill, is called to the emergency room of a California hospital, where a screaming man is being held in custody. Dr. Hill agrees to listen to his story. The man identifies himself as a doctor, and recounts, in flashback, the events leading up to his arrest and arrival at the hospital.
In the nearby town of Santa Mira, Dr. Miles Bennell sees a number of patients apparently suffering from Capgras delusion—the belief that their relatives have somehow been replaced with identical-looking impostors. Returning from a trip, Miles meets his former girlfriend, Becky Driscoll, who has recently come back to town after a divorce. Becky's cousin Wilma expresses the same fear about her Uncle Ira, with whom she lives. Psychiatrist Dr. Dan Kauffman assures Bennell that these cases are merely an "epidemic of mass hysteria."
That evening, Bennell's friend, Jack Belicec, finds a body with his exact physical features, though it appears not fully developed; later, another body is found in Becky's basement that is her exact duplicate. When Bennell calls Kauffman to the scene, the bodies have mysteriously disappeared, and Kauffman tells Bennell that he is falling for the same hysteria.
The following night, Bennell, Becky, Jack, and Jack's wife Teddy again find duplicates of themselves, emerging from giant seed pods in Bennell's greenhouse. They conclude that the townspeople are being replaced while asleep with exact physical copies. Miles tries to make a long-distance call to federal authorities for help, but the phone operator claims that the long-distance lines are dead or busy. Jack and Teddy drive off to seek help in the next town. Bennell and Becky soon realize that all of the town's inhabitants have been replaced and are devoid of humanity. They hide at Bennell's office for the night, vowing to stay awake.
The next morning, Bennell and Becky watch from the office window as truckloads of the giant pods arrive in the town center. They listen as Nick Grivett (the chief of police) directs the others to take them to neighboring towns to be planted and used to replace their populations. Kauffman and Jack, both of whom are now also "pod people", arrive at Bennell's office with new pods for Becky and Bennell. They reveal that an extraterrestrial life form is responsible for the invasion; the pods, capable of replicating any life form, traveled through space and landed in a field. After their takeover, Kauffman explains, humanity will lose all emotions and sense of individuality, creating a simplistic, stress-free world.
After scuffling with and knocking out Kauffman, Jack, Grivett, Bennell, and Becky escape the office. Outside, they pretend to be pod people, but Becky screams at a dog that is about to be hit by a car, exposing their humanity. A town alarm is sounded, and they flee on foot, pursued by a mob of pod people.
Exhausted, they manage to escape and hide in an abandoned mine outside town. Later, they hear music, and Bennell leaves Becky briefly to investigate. Over a hill, he sees a large greenhouse farm with hundreds of giant seed pods being loaded onto trucks. Bennell returns to tell Becky, and upon kissing her, he realizes, to his horror, that she fell asleep and is now one of them. Becky sounds the alarm as he runs away. He is again chased by the mob, and eventually finds himself on a crowded highway. After seeing a transport truck bound for San Francisco and Los Angeles filled with the pods, he frantically screams at the passing motorists, "They're here already! You're next! You're next!"
The flashback ends with Bennell finishing his story back at the hospital. Dr. Hill and the on-duty doctor step outside the room, the latter expressing his certainty that Bennell is psychotic. A truck driver is wheeled into the hall after being badly injured in an accident. The orderly tells the doctors that the man had to be dug out from under a load of giant seed pods. Finally believing Bennell's story, Dr. Hill calls for the police to block the roads in and out of Santa Mira, while he alerts the FBI.