Small-town doctor Paul Beecher (John Beal) is given some strange pills by a dying elderly researcher. Later, when Paul gets a severe headache, his young daughter accidentally gives him the mystery pills. He's later puzzled by a series of strange deaths in which all the blood was drained from the bodies of the victims and then discovers the old researcher was working on a project involving vampire bats. The horrified Paul gradually begins to suspect that he himself is the killer.