Les Diaboliques

The film Hitchcock tried to buy and missed by hours, after which he bought Psycho instead.

A headmaster's wife and his mistress conspire to kill him. They do. The body will not stay where they put it.

Clouzot shoots a boys' boarding school as a place of permanent damp and bad food, and the school is the point: everything happens in institutional corridors under bad light, with children present.

The bathroom sequence is the one, and it is the direct ancestor of every reveal in this category.

The end titles ask the audience not to spoil it for people who have not seen it, which was almost unheard of in 1955.

Clouzot's treatment of Véra Clouzot, his wife, during the shoot was reportedly brutal. She died of a heart attack five years later at 46.