The fourth of Hammer's psychological thrillers, made to capitalise on the success of films like Psycho and Les Diaboliques. It is one of Freddie Francis' most imaginative films, making the most of a patchy Jimmy Sangster script. Knight (a faceless Hammer lead) is the suspect hero, and Linden the tormented young heroine haunted by the fear of hereditary insanity who, as the film begins, is plagued by a recurring nightmare in which her mother lures her into a mental asylum. Normally the Hammer psychological strain has a disconcertingly contemporary tone, but here the apparatus (who is trying to drive the girl out of her mind?) is truly Gothic: old country house, absent guardian, white phantom, etc.