Once inseparable, Fanny, Thomas and Maxime have never spoken to each other since Vinca disappeared that winter night in 1997. We soon learn that that same night Vinca disappeared, Thomas and Maxime murdered their philosophy teacher, Alexis Clément. . Maxime's father, Francis, and his right-hand man Ahmed, immured the body in the high school gymnasium which will be destroyed in the coming days. When, 25 years later, Thomas decides to break this silence by going to a reunion of former students of the Saint-Exupéry high school, he will, without knowing it, put the lives of all those around him in danger, start with that of Maxime. How will the two friends manage to cope with the situation?

Francis is kidnapped from his home by a masked individual. Fanny confesses to Thomas that she was Vinca's accomplice. She asked him to take pictures of her and Richard in order to blackmail him. For his part, Maxime is under pressure from the "unreliable friends" of his father Francis. His father being unreachable, it is now up to Maxime to repay this debt. Pianelli learns from hospital staff that Ahmed died shortly after conjuring up a body in the gymnasium wall. Suspicion immediately turns to Fanny...