"Les Diaboliques" (1955)

A superb French horror-thriller. It's a simple premise: two women plot to kill a sadistic headmaster of a boys' school; one is his wife, the other his mistress. There isn't a moment without palpable suspense as the director, Henri-Georges Clouzot, has total command of the storytelling, twists piling upon twists, all ending in a shocko ending. This movie does for baths what "Psycho" did for showers. Your screaming will feel so good, catharsis can do that.