May 1953. From the skies over Santa Mira, California drift pods from outer space. A few short months later, something strange seems to be happening to some of the town’s residents. What is described as a “contagious neurosis” has several townspeople behaving strangely with their insistence that loved ones and friends are not really their loved ones and friends. Oh, sure, they may look like the people they know, but they aren’t the people they know. Crackpots?
Dr. Mile Bennell thinks so until, one night he and his one-time girlfriend Becky Driscoll are called to visit their friends Jack and Theodora Belicec. Seems that the Belicecs are not busy cheating at football, but are instead trying to figure out what is the deal with a half-formed body on their billiards table. The body is not just unformed, but doesn’t even possess fingerprints. As they try to figure out what to do about it, Theodora screams that it is Jack. Sure enough, the body is taking shape and the form is going to look just like Jack.
Mile takes Becky home and finds that she also a duplicate of herself in her home. He goes to get help, but upon returning, the copy of Becky has disappeared. Meanwhile, so has the copy of Jack.
The small town’s resident psychiatrist, Manfred Kaufman, has been helping those who have made complaints that the people they love aren’t really the people they love. Miles, Becky, Theodora and Jack head to the doctor’s house to see if he can offer any explanation for the macabre duplicates, but instead they find four bodies that being forming into the four of them. Miles injects air into the veins of the forming bodies which causes them to turn into gray wispy figures they deemed “tumbleweeds.” When Miles tries to phone the FBI, it becomes obvious that the duplicates have taken over the phone lines. It’s worse than that: the duplicates—who look and sound the same as the real thing but express no capacity for feeling or having emotions or individual personality—have taken over all of Santa Mira. Those not yet duplicated inside the pods are being rounded up so the process can be forced upon them.
Miles and Becky head for the office of Manfred Kaufman only to discover that he was one of the very first to become a “pod person.” Not only that, but Kaufman has been instrumental in the process of getting pods into the homes of Santa Mira’s residents. He also relates how the aliens arrived by Earth purely by chance and originally made the somewhat humorous mistake of duplicating a tin can and handle of an axe because both contained organic material before they realized the vital significance of humans in going about their plans for invasion: to use of every last living organism on the planet before moving onto the next world.
Now it’s turn for Miles and Becky to be assimilated. Kaufman has their pods placed into the doctor’s office in which they are locked. Miles places the doctor’s skeletons near the pods to fool Kaufman and his scientist buddy Budlong and when the two return, they are jumped from behind as Miles injects them both with morphine. Becky joins Miles as they make a run for it by acting like their fellow automaton duplicates. Their plan is merely to make it safety to the highway outside of town and hitch a ride so they can alert the authorities, but they change strategy upon arriving at a field full of pods that are being farmed for export out of town.
After pouring gasoline into the irrigation ditch running alongside the field, the entire pod farm goes up in flames and the flames uproot the pods who rise into the atmosphere until they disappear from sight. At the exist of the pods, the human duplicates suddenly seem to lose any conscious guidance and merely walk around aimlessly like zombies with no fresh brains to eat.
Miles and Becky make their way back home and discover that the Belicecs also managed to avoid duplication. Shortly thereafter, Becky becomes Mrs. Bennell, the pod people die off and Santa Mira is repopulated by new citizens moving in.
