In the most Hitchcockian of all the films made by the French master of suspense - like Vertigo, it was adapted from a novel by Boileau and Narcejac - the wife and the likewise abused mistress of the tyrannical headmaster of a seedy boys' boarding school conspire to put an end to his callous brutality. Taut as a mantrap, the meticulous script provides plenty of tension, surprises and shocks, but what really distinguishes the film is Clouzot’s beady eye for details both atmospheric and telling: a swimming pool clogged with debris, rancid school meals, the dismal efforts of the staff to curry favour. Much imitated but seldom bettered, the film can also lay claim to a clutch of excellent performances; not just Véra Clouzot, Simone Signoret and Paul Meurisse as the misbegotten ménage-à-trois, but a young Michel Serrault as a teacher and the inimitable Charles Vanel as a canny detective.