Mysterious puzzle of who or what is behind a young girl, having just returned from a boarding school in the English countryside, becoming increasingly paranoid and psychotic. The girl witnessed her mother killing her father years ago and has nightmares of the event. She believes that she has the same mania and starts seeing her mother, other apparitions, and various things connected with the event that happened on her birthday so long ago. She is heir to the house, but her uncle manages her estate. A nurse is supplied for her and the home is run by an elderly couple of servants that have been with the family for a long time. What starts out as something you keep thinking you have seen before - swiftly and adroitly changes direction and becomes something I had never seen before. This is above all a well-crafted film made with creating suspense and maintaining suspense as its primary objectives. Director Freddie Francis, the Hammer stalwart, directs with his usual keen, meticulous detail for the lens. He paces the film very nicely, and he is aided by very good performances from all concerned. The real credit for the film's success though must go to veteran Hammer writer Jimmy Sangster. Above all this is a script-driven vehicle. Certainly one of the lesser known Hammer horror films but definitely one of the better psycho films I have seen.