Camille is behaving oddly at home with Jess, Ulysse and Caillou, the dog, but also with the team, puzzled by her suggestions and reactions. She is also trying to destroy Adèle's life and reputation, while Adèle, locked in UMD (Unité pour Malades Difficiles) in her place, is not able to prove she is the victim of a plot. The team investigates the murder of Lionel Dugain, 28, Maths professor, by a shotgun. Dugain had encouraged Agathe's parents to settle in Yonne. Rocher, worried for Lucas is having nightmares more frequently, learns that the place, where his son had spent a week with Agathe's family, is a refuge for problem children.