Rousseau, a crime novelist from Paris, is summoned to the monastery in Mouthe. There, Brother Giacomo, who knew David's deceased mother, has something important to tell him. But when the author arrives, Brother Giacomo has recently died.
Crime writer David Rousseau was right to suspect a serial killer: After the postman's body was dressed up as Vincent Van Gogh, the next victim was a replica of Marylin Monroe.
After Major Louvetot of the gendarmerie is in the dark with his research, he finally takes up Rousseau's theory: Suspicions point to Hugo, the librarian.
The culprit seems to be playing a game of cat and mouse with Louvetot and Rousseau and enjoys leading everyone around by the nose. They arrive just in time to save Aurélie.
David Rousseau is saved at the last minute by Louvetot. Now all that remains is to find Lyes and Niki, and to render Aurélie harmless. But so close to the goal, the colleagues from the nearby county seat take over the case.
