Don Siegel's classic exercise in psychological science fiction has often been interpreted as a cautionary fable about the blacklisting hysteria of the McCarthy era. It can be read as a political metaphor or enjoyed as a fine low-budget suspense movie, and it works well either way. Kevin McCarthy stars as Miles Bennel, a doctor in the small California community of Santa Mira, where several patients begin reporting that their loved ones don't seem to be themselves lately. They look the same but seem cold, emotionally distant, and somehow unfamiliar. The longer Miles looks into these reports, the more stock he places in them, and in time he makes a shocking discovery: aliens from another world are taking over Santa Mira, one citizen at a time. Emissaries from a distant planet have sent massive seed pods containing creatures that can assume the exact physical likeness of anyone they choose. When Santa Mirans go to sleep, the pod creatures take on the shape of their victims and then destroy their bodies. The aliens may look the same, but they possess no human emotions and, like plants, are concerned only with propagating themselves and eventually subsuming the earth. Needless to say, Miles and his friends are terrified, but since it's hard to tell who's a person and who's a pod, they're at a loss for what to do, especially when it seems that there are increasingly more aliens than humans.