Ludovic and Nathan discover that the violent boyfriend of Nolwenn, the third victim, is the son of a jeweler from Brest... Could it be the mysterious murderer with the ring? While Nathan pursues this lead, Ludovic observes with horror the disappearance of Parvana and Sam: Mélanie, by provoking a meeting with Parvana in 1998, has changed the future! The young woman feels terribly guilty: how is she going to make up for her mistake?

Mélanie is devastated when she learns that it is most likely Nathan, her husband's friend and teammate, who will assassinate him in a few hours... She has one last request: to meet her daughter whom she has not seen to grow. In 2025, Parvana has followed through on her threats and left home with Sam. To make matters worse, Ludo finds himself removed from the investigation. Will Ludovic and Mélanie manage to prevent the inevitable?