Investigating the murder of a street artist, Cannes detective Camille Delmasse keeps running into the suave but shady Harry King; Camille's father, the former chief of police, is set to be cleared of corruption until secrets upend events.

When a casino owner's wife is poisoned, suspicions fall on blacklisted gambler Roxie Roland; Camille turns to Harry for help, for who better to bring down a con woman than a con man; Harry discovers the name of the man threatening Camille's father.

A monk is found murdered below an island fort; Camille and her partner, Lea, delve into the victim's dark past for answers, with input from Harry's old friend, who was the monk's mentor; a ruthless fixer named Julien Boire threatens Camille's sister.

Camille goes to see her father in prison despite efforts to intimidate her. Ordered to protect a visiting billionaire who has had death threats made against him, she and Lea turn to Harry for intel about a legendary assassin known as the Nightshade.

When Pascal Fontaine is found hanged after a séance, it seems he's the victim of a curse related to the family matriarch's death in a mental asylum; the team deal with shady mediums and scorned lovers, while Harry and Camille set a trap for Boire.

The death of an actress's assistant during the Cannes Film Festival could be an accident or murder, and the case affects Lea deeply; with his daughter at risk, Harry decides to stop Boire once and for all, but what he learns will devastate Camille.