Takabe is a Tokyo detective who is investigating a series of brutal murders in which each victim is found with an "X" carved into their chest. Their killers are apprehended nearby in a trance-like state with no memory of their acts. Takabe enlists the help of a psychiatrist to establish a link between the murderers. After struggling with the evidence, they hit upon a young psychiatry student, Mamiya, who had a connection with one of the killers. They soon conclude that Mamiya had been working with hypnosis and planted the idea to kill into his subjects' minds. However, Takabe's attempts to interrogate Mamiya are thwarted by the suspect's knowledge of Takabe's personal problems.