Les Diaboliques, released as Diabolique in the United States and variously translated as The Devils or The Fiends, is a 1955 French black-and-white psychological thriller feature film directed by Henri-Georges Clouzot, starring Simone Signoret, Vera Clouzot, Paul Meurisse and Charles Vanel. It is based on the novel Celle qui n'etait plus (She Who Was No More) by Pierre Boileau and Thomas Narcejac. The story blends elements of thriller and horror, with the plot focusing on a woman and her husband's mistress who conspire to murder the man; after the crime is committed, however, his body disappears, and a number of strange occurrences ensue. The film was the 10th highest grossing film of the year with a total of 3,674,380 admissions in France.
Clouzot, right after finishing Wages of Fear, snatched the screenplay rights from Alfred Hitchcock. This movie helped inspire Hitchcock's Psycho. Robert Bloch himself, the author of the novel Psycho, has stated in an interview that his all-time favorite horror film is Diabolique. In 2007, Time placed Les Diaboliques on their list of Top 25 Horror films. In 1954 Les Diaboliques won the Louis Delluc Prize and the award for best foreign film at the New York Film Critics Circle Awards in 1955.
(Summary from Wikipedia)