Professor Artus, a scientist specializing in artificial life, wants to try an experiment on an automaton; he is entrusted with a death row inmate. The professor is soon found murdered. It is Inspector Wens, helped by a journalist, who must solve the case. Franck Villard in the role of Wens succeeds Fresnay.

Fleeing Paris where he killed, Olivier takes refuge in the Giraud farm and falls in love with his daughter, to the chagrin of her suitor, a man named Joseph. When the latter is found dead, Olivier is accused and the young woman will arrive too late to clear him, the poor man having fallen into a ravine while trying to flee.

In an isolated house, in Brittany, live two sisters around whom gravitate a whole series of strange characters. Between the eruption of the vagrant voyeur and that of the couple in love, the youngest kills her eldest and goes mad.

"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.