In Avalone, it's shocking. In place of the little girl believed to be dead, stands a young woman, radiant and very much alive. The investigation then takes a new turn. Elsa explains her strange disappearance, revelations that take Romain back 23 years and deeply destabilize him. Will Noémie manage to shed light on this strange cold case? And will she succeed, through this investigation and Hugo's unwavering help, in overcoming her own personal drama... and perhaps breathing new life into her life?

Another corpse, that of an adult, throws the investigation into disarray. Who could this woman be, found in a grave that isn't hers? Upset by his mother Catherine Valant's revelations, Romain struggles to keep his cool and could well be sidelined from the investigation by Noémie... who, for her part, decides to finally face her own demons by agreeing to a dive with Hugo. A surprise visit from the prosecutor could then definitively put an end to Captain Chastain's mission... if it weren't for the unexpected and surprising appearance of someone we never thought we'd see return to Avalone...

As Jean Casteran emotionally explains his illicit activities, a devastating fire breaks out at the Dorin farm, the parents of little Alex. Jacques Dorin is the ideal suspect, and the team focuses on his actions, pushing him to his deepest limits. At the lake, all the barrels are brought to the surface, and the village can finally bury its dead. But one mystery still remains... What happened to little Elsa, whose body has not been found?

During Hugo's latest dive, an extraordinary event occurs in the submerged city. This catastrophe nearly claimed a life. Noémie is far more affected than she admits by this investigation, which brings back a childhood trauma. At the home of Jean Casteran, Cyril's father, Noémie and Romain unearth a diary that belonged to the missing little boy. His childhood words directly incriminate his father and constitute new evidence of his potential guilt. But the man is suddenly nowhere to be found...

The body is identified as little Alex Dorin. Tensions are rising in the city because at the time, three children were missing: Alex, but also Cyril and Elsa, who were Lieutenant Romain Valant's best childhood friends. Noémie's teammate is devastated, but is determined to continue the investigation...

Assigned to a police station in a small town in Occitanie after an operation that disfigured half of her face, Parisian police captain Noémie Chastain sees her forced convalescence mission take a dark turn. While she was supposed to report on the police station's activities and its possible closure, she suddenly finds herself plunged into a missing persons case dating back twenty years. A barrel containing the skeleton of a child rises to the surface of the artificial lake, at the bottom of which lies the ancient submerged village. Despite her superiors, who consider her fragile, the captain takes this case head on. But through this strange investigation, she will see a whole buried part of her own life resurface as well...