An astronomer discovers a spherical spaceship which is then buried under tons of rock, and nobody believes that he really saw it. Shortly after that, some people in town start acting strangely. Soon it is discovered that they have been replaced by aliens from the spaceship.
Despite the fact that I don't care for some of the changes in dialogue that were made in the rewrite of Ray Bradbury's original script, and that it contains at least one godawful moment (a bogus scare involving a kid in a spaceman outfit), this is my second favorite Jack Arnold movie. The fact that both the humans and the aliens have a fear and dread of each other is something I found uncommon in many SF movies, but it makes the movie seem that much more real. It also has a nice poetic touch, with some truly eerie and memorable images that stick in the mind. I was fortunate enough to see this one in 3D during the revival in the eighties, but this is one of those movies that doesn't really need it. This is indeed one of the most important SF movies of the fifties.