马克（卡尔亨兹·伯恩 Karlheinz Böhm 饰）是一名摄影师，热爱摄影的他随身都携带着他父亲留给他的一台手持摄影机。一起连环杀人案件在城中引起了恐慌，被害者均为女性，死去时，她们的脸上布满了极为恐惧的表情，而仪表堂堂的马克，就是犯下这些可怕罪行的真凶。原来，马克的父亲是一位研究儿童恐惧的心理学家，作为他的实验对象，从小马克就被各种各样突如其来的惊吓所包围，这样长久的恐惧和压抑导致了他扭曲的性格，也成为了一切惨剧的导火索。 　　一次偶然，马克被邻居海伦（安娜·玛西 Anna Massey 饰）的美貌所吸引，正当他准备对海伦下手时却犹豫了。海伦的天真美好暂时治愈了马克的童年创伤，但时常肆虐的疯狂却又让他陷入了与天性的自我纠葛中。接连犯案的马克引起了警方的注意，而在被捕之际，绝望的马克选择了自我毁灭。Mark Lewis, works as a focus puller in a British film studio. On his off hours, he supplies a local porno shop with cheesecake photos and also dabbles in filmmaking. A lonely, unfriendly, sexually repressed fellow, Mark is obsessed with the effects of fear and how they are registered on the face and behavior of the frightened. This obsession dates from the time when, as a child, he served as the subject of some cold-blooded experiments in the psychology of terror conducted by his own scientist father. As a grown man, Mark becomes a compulsive murderer who kills women and records their contorted features and dying gasps on film. His ongoing project is a documentary on fear. With 16mm camera in hand, he accompanies a prostitute to her room and stabs her with a blade concealed in his tripod, all the while photographing her contorted face in the throes of terror and death. Alone in his room, he surrounds himself with the sights and sounds of terror: taped screams, black-and-white "home movies" of convulsed faces. At his house, he meets Helen Stephens, a young woman who lives with her blind mother in a downstairs flat. She visits his flat, where he shows her black-and-white films that were taken of him when he was a child. She is horrified to see that his father used him as a guinea pig in various experiments, taking movies of his reactions of fear.