In a garage under Place Vendome, firemen find a burnt corpse behind the wheel of his car. The cops identify Philip Roquin, an accountant at a jewelry store. Being told about the tragedy, his family and employer's testimonies differ: the latter hasn't heard of Philip in two weeks while his wife tells the cops he has been in a car accident. Having found the killing was perpetrated following a kidnap and ransom, Jo tracks back Philip's trail to discover Lisette, a woman he was having an affair with, which might have led him to his death. In a race against time to save the next kidnapping victim, the investigation leads Jo to a prison where Lisette had spent time and a warden who has strange relationships with the inmates.

On a sunny afternoon after taking his daughter to her ballet lesson, a middle-aged man gets stabbed on the steps of the Palais Garnier. The victim is an economist and a family man, and everything suggests the murder was random. Soon after however, a teaching assistant to a Political Science professor is found stabbed to death in a similar fashion on a subway train at Barbes-Rochechouart Metro station. Jo finds out that the two murders have parallels in political crimes history and the victims are linked with a mysterious Political Science grad student.