An enjoyable mystery movie for its period. I’ve never seen the remake, but I suspect it is not as good, as the plausibility of the plot was highly dependent upon a more naïve movie audience.  - DG

Les Diaboliques (1955), directed by Henri-Georges Clouzot

From Wikipedia
Les Diaboliques (The Devils), also known as The Fiends or Diabolique, is a 1955 black and white French suspense film directed by Henri-Georges Clouzot, starring Simone Signoret, Véra Clouzot and Paul Meurisse. It was based on the novel Celle qui n'était 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.