Diabolique, 1955

At a seedy French boarding school, The headmaster (Paul Meurisse) tyrannizes both his fragile wife (Véra Clouzot) and his no-nonsense mistress (Simone Signoret). They plot to kill the bastard, drowning him in a bathtub and dumping his body in the school swimming pool. Then a few students say they've seen him; the drained pool yields no corpse; and one night, when she's alone, the wife hears familiar typing in her late husband's room... Henri-Georges Clouzot directed this dank, peerless exercise in nerve-jangling.