The wife and mistress of a sadistic boarding school headmaster plot to kill him. They drown him in the bathtub and dump the body in the school's filthy swimming pool... but when the pool is drained, the body has disappeared - and subsequent reported sightings of the headmaster slowly drive his 'killers' (and the audience) up the wall with almost unbearable suspense...

Les Diaboliques is a 1955 black-and-white film directed by Henri-Georges Clouzot, starring Simone Signoret and Véra Clouzot. The title translates as 'The Devils'. It was called The Fiends when released in the UK, while the US release is entitled Diabolique. It is based on the novel Celle qui n'était plus by Pierre Boileau and Thomas Narcejac. Boileau and Narcejac, are credited with early use, if not coinage, of the term film noir, which has also been used to describe Les Diaboliques.[citation needed]

Variously described as a "mystery" a "thriller" and even a "horror film," the film created a sensation on its original release. It has often been likened to the films of Alfred Hitchcock in that it is still creepy even when one has seen it and knows the ending. The end credit contains an early example of an "anti-spoiler message", requesting the audience not to disclose the plot to others who have not seen the film.

The film gained additional press when only five years after its release, Véra Clouzot died of a heart attack at age 47, similar to the way her character in the film died.