Several notables from the Chamonix region are found murdered in their homes. To move forward with investigation, police captain Thomas Delhaye decides to release Juliette Hémon from prison, imprisoned for a strangely similar case.

In a French thermal town, a man is found poisoned. His ex-girlfriend is arrested for the murder but her estranged cop daughter tries to prove her innocence which leads her much further than she could have ever imagined.

Elisa, a fiery and passionate teenager, wants to enjoy the summer of her 17 years on the steep slopes of the Vercors where she grew up. But her mother leaves the house and leaves her alone with her father to look after her disabled sister. An increasingly heavy responsibility that makes love switch to hatred.

In the city of Lyon, despite the police's best efforts, an elusive assassin is targeting ordinary citizens. They all share one thing in common: suspected of serious crimes, they have all managed to escape justice. In the press and among some of the public, a name is circulating: "The Vigilante." A local police commissioner and a somewhat self-important Parisian profiler, Marie Sainz and Claire Legendre, team up to try and unmask and stop this overconfident killer.

Annecy. When Valentin Poncet, an exemplary firefighter with a remarkable past, is found dead in suspicious circumstances, Commissioner Cassandre and her team must untangle the threads of a murder that appears to be linked to a burglary. Between the discovery of a mysterious fiancée Val may have had, the shadow of a dangerous arsonist looming overhead, and tensions within the fire station—still reeling from this second recent tragedy—each clue raises new questions and sheds light on a tragic family history with deeply buried secrets.