Kurt is just over 20-years-old and has an accent that is hard to place. Lea is younger and more shy. The two meet one summer at the seaside and have an affair. Kurt is a taciturn loner who steals cars, is responsible for a number of strange break-ins, and lives from his ill-gotten gains, spending his money on arms and ammunition. Detective Thomas is in charge of the investigation of a series of crimes including the murder of a police officer in Savoy, various break-ins, the kidnapping of a woman, and the disappearance of a man in Sisteron. Convinced at an early stage that these deeds are all the work of a single individual, he formulates the theory that the culprit is a madman, perhaps an Italian. Thomas's interest in the case soon reaches the level of an obsession.