Invasion Of The Body Snatchers (1978) [movie trailer]
In deep space, a race of gelatinous creatures abandon their dying world. Pushed through space by the solar wind, they make their way to Earth and land in San Francisco. The city falls under extraterrestrial influence making it difficult to tell who is human, and who is an imposter. A good classic, scary story. Starring Donald Sutherland, Veronica Cartwright, Jeff Goldblum and Leonard Nimoy: