This 35mm screening, also being shown on August 14th, is part of the Jean-Pierre Melville season at BFI Southbank. You can find full details here.
Chicago Reader review:
Sex, religion, and blackmail feed the cauldron of this early thriller (1953) from Jean-Pierre Melville, the French cinema’s preeminent misanthrope. A young novitiate (Juliette Greco) is called home to watch over her younger sister (Irene Galter) after their parents are killed in a car accident, and when the sister is raped by a handsome drifter (Philippe Lemaire), the former nun comes after him packing more than a rosary. The atmosphere is so thick with lust and vengeance that any Catholic reading of the story is impossible; here the Church is just another shadowy institution, where people hide from their own evil.
Here (and above) is an extract.