In a small Swiss resort town, sisters Anne (Janet Munro) and Sarah Pilgrim (Jennifer Jayne) are worried by Anne's telepathic sense, which goes haywire. Reporter Philip Truscott (Laurence Payne) and U.N. worker Alan Brooks (Forrest Tucker), who's in the area to investigate unusual radiation levels, also sense something is amiss. It turns out vicious extraterrestrials are living in a radiation cloud in the Alps, brutally killing anyone who comes near and threatening to descend upon the town.