As a boy, Mark Lewis was subjected to bizarre experiments by his scientist-father, who wanted to study and record the effects of fear on the nervous system. Now grown up, both of his parents dead, Mark works by day as a focus-puller for a London movie studio. He moonlights by taking girlie pictures above a news agent's shop. But Mark has also taken up a horrifying hobby: He murders women while using a movie camera to film their dying expressions of terror. One evening, Mark meets and befriends Helen Stephens, a young woman who rents one of the rooms in his house. Does Helen represent some kind of possible redemption for Mark - or is she unknowingly running the risk of becoming one of his victims?
Karlheinz Böhm ... Mark Lewis
Moira Shearer ... Vivian
Anna Massey ... Helen Stephens
Maxine Audley ... Mrs. Stephens
Brenda Bruce ... Dora