In the Cévennes, Jonas, leader of a scout camp is found dead in a Protestant temple, a syringe in his hand. Everything suggests that it is not an overdose but a murder in disguise. To solve the investigation, Captain Elli Talleb is associated, not without surprise, with the new criminology expert in the region: Father Clément Desmoulin. Indeed, freshly graduated in psycho-criminology, Clément nevertheless remained in orders. He has extended his novitiate and sees his experiences outside the monastery as a test of his spiritual commitment. The search for the culprit of this murder will put the nerves and feelings of Elli and Clément to the test, decidedly an odd couple of investigators.