The first English-language film of director Roman Polanski is a psychological thriller in the vein of Alfred Hitchcock's Psycho (1960) and his own later film Rosemary's Baby (1968). Catherine Deneuve stars as Carol Ledoux, a Belgian manicurist living with her sister, Helen (Yvonne Furneaux), in a London flat. Simultaneously attracted and repulsed by sex, Carol is a virgin who finds her sister's relationship with a married man, Michael (Ian Hendry), extremely disturbing. When her sister and Michael go on holiday, Carol begins to disintegrate mentally, hallucinating bizarre encounters, being forced into taking a sabbatical from her job and ultimately committing a pair of murders in her deranged state.