A woman is found dead in the steam room of a spa. She looks 20 years younger than she is. Investigations take Niémans and Delaunay to the next village.

Niémans and Delaunay explore the dark side of the human soul, along a road dotted with unexplained deaths. Their bond strengthens when Camille's son gets into a desperate situation.

Camille finds a cryptic note from the killer in her jacket. A second murder occurs while relics are stolen from a nearby town.

The body of a black woman is discovered with a hash symbol carved into her forehead. Investigations lead the detectives to a migrant camp.

Camille meets the Professor, an authority figure at the camp. When a second body is found, the mystery deepens. A demon myth is terrifying the migrant camp. His calling card is a carved hash symbol.

The butler of the Monferville estate finds a 17-year-old in a pitiful condition. The teenager claims to be Herminien, a son of the family who disappeared 6 years ago. Camille is looking for her son Léo.

Camille suspects her son Léo is pretending to be the missing boy. What a shock when the grieving mother confirms that the boy is Herminien. The case takes a new turn when a DNA test reveals no match between Camille and Léo.