Diabolique (1955)

In this classic of French suspense, the cruel and abusive headmaster of a boarding school, Michel Delassalle, becomes the target of a murder plot hatched by an unlikely duo — his meek wife and the mistress he brazenly flaunts. The women, brought together by their mutual hatred for the man, pull off the crime but become increasingly unhinged by a series of odd occurrences after Delassalle’s corpse mysteriously disappears.