"1950s science fiction" is a term that conjures images of aliens, giant bugs, and cheesy special effects. Most of these movies were silly trifles, but Invasion of the Body Snatchers is a rare one that gets away with an outrageous premise thanks to sharp dialogue and how it plays upon deep-rooted fears. The best horror movies strip away those things we find most secure. This one speculates on what it would be like if your loved ones -- your spouse, parents, siblings, people you've known all your life -- were suddenly not the same. They look the same, act the same, sound the same, and yet are somehow critically different.

Kevin McCarthy plays a doctor in a small town who becomes increasingly suspicious about widespread reports about people being disturbingly different somehow. The situation escalates rapidly from there. Don Siegel, who went on to direct Dirty Harry 15 years later, keeps the film tight and taut with near perfect pacing and drives its impact home with some unforgettable visuals. Much speculation has been made about whether the film is a metaphor for McCarthyism, then in high gear, or perhaps a cautionary tale about communism. While it's fun to entertain these notions -- and the fact that one can do so is a testament to the film's complexity -- it works best at face value, as a speculative work of horror.

The film's book-ends, incidentally, were not in the original script. The studio demanded the prologue and epilogue to keep the film from being too downbeat. Some rereleases do not have this footage. The film is not injured much with it, but it does work better without it, not so much for reasons of tone but logistics.