A provincial magistrate suspects that a tramp picked up by the police for molesting a young country girl, is the murderer of several young shepherds. The man feels himself driven by a strange frenzy, and calls himself the Anarchist of God. The magistrate slowly breaks down the tramp through interrogation, and discovers that he had tried to kill a girl he was in love with and then to shoot himself, although both of them survived. After that, he began his travels through France, committing a series of murders in lonely country areas.

The story is based on the actual existence, in the last part of the nineteenth century, of a criminal who was once a monk and later a sergeant in the French army, who took to random killing of country people.