The story opens in the present day, at a high school reunion in the south of France where three former friends reconnect. They grew apart and lost touch, but they are still bound by a tragic secret tied to the disappearance of a high school girl who went missing 25 years ago in the region.
Four friends go to a party before the Christmas holidays. But Vinca cancels and later, in distress, calls Thomas. He rushes to school but she is gone, for good. 25 years later, Thomas receives a threatening invitation to a school reunion.
Thomas and Max visit Francis to tell him the police have found Clement's body. Francis says he has engaged a Russian gang to recover the evidence. Meanwhile, Manon finds 100,000 francs in an old gym locker. Thomas pretends incredulity.
Francis is kidnapped. Fanny admits that Vinca asked her to take pictures to blackmail Richard. One of Max's daughters is taken by the Russians. Pianelli hears of Ahmed's death, shortly after his revelations about the walled-up body.
Max breaks down and confesses to Annabelle. When Thomas looks to find traces of the other Alexis, he finds traces of a secret house, belonging to Francis and Annabelle, and more. Meanwhile, Francis is beaten and interrogated by hooded men.
Thomas is in mourning, his father is dead and his half-brother is in a coma. He no longer understands anything and Annabelle tells him Fanny has all the answers. Revelations from Fanny put Thomas on the trail of the real Alexis.
We go back 25 years and finally experience the events from Vinca's point of view. Back in the present, Annabelle confronts DeVille with a gun about the attacks on Francis, Ahmed and Max.
