1998: after shooting Nathan, Melanie takes refuge with Hector, her high school friend, before realizing that she has just thrown herself into the mouth of the wolf! 2025, Ludo will still confront Hector, at his own risk.

Melanie 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.

While Parvana and Ludovic are together again - as well as Florence and Nathan - another butterfly effect appears: Commissioner Ben Salem is now one of the victims! For his part, Ludo is convinced that M?

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?

Zo? Levy and M?lanie wore the same ring when they died: it is now certain, they have a common attacker... who must have had other victims! At the same time, M?lanie's change of attitude in 1998 has devastating consequences for the future: Nathan, colleague and friend of Ludo, and Florence, M?lanie's friend, have not met... They have destroyed their family! Ludo panics: if Melanie survives, what will happen to Parvana and Sam?

Brest, 2025. Ludovic B?guin, police captain, investigates the death of a woman found drowned on the beach of Corsen. In a virtual reality room to re-study the crime scene captured by drones, Ludovic discovers that he can come into contact with M?lanie, his wife.