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 reproducing a duplicate replacement copy of each human. As each pod reaches full development, it assimilates the physical characteristics, 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.

References:
https://en.wikipedia.org/wiki/Invasion_of_the_Body_Snatchers