As famous for the gimmick with which the film was shown as for its genuinely spine-tingling story, The Tingler follows a pathologist (Vincent Price) as he searches for the cause of a series of deaths and discovers that the victims have a large insectlike creature growing on their spinal chords. The creature attacks when the people are frightened and are only killed when the host emits a blood-curdling primal scream. This is coupled with a subplot to scare the deaf-mute owner of a silent movie house to death. Along the way, a couple of characters are injected with LSD and begin hallucinating like mad. The show stopper came when one of the nasty monsters "escaped" into a movie theater. The gimmick is one of director William Castle's most famous. In order to further frighten audiences, he had certain theater seats rigged with small Army surplus devices that would deliver a mild electric shock to the spine in hopes of inducing terrified screams. If no audience member screamed, then Castle had a back-up plan in which a planted audience member would scream and faint. The house lights would go up, the film would stop and ushers would carry the unconscious person out of the theater.