Stain on the Snow.

"La neige était sale" is based on a novel and play by the phenomenally prolific Georges Simenon. Upon learning that his mother was a prostitute, Frank (Daniel Gélin) dejectedly vows that he, too, will live a life of debauchery. Part of his self-degradation program is to kill someone, and since the story takes place during the Nazi occupation of France, he chooses a German officer as his victim. His steady descent into psychosis and depravity becomes his ultimate undoing.