A man's body is found on a building site. The victim was a private detective. While he is struggling to recover from the investigation into the crossbow killer, Martin prematurely returns to work to pursue this new case. Especially as other murders, apparently without motive, are soon reported...

Véronique Legat is removed, held captive, stripped, then released. Six other women looking like her have disappeared over the last 5 years. Martin and Jeannette begin their investigation with the husband of the first missing woman. Quickly, they are convinced that these women are dead. But why was Véronique spared?

"Save my children". These are the last words of a woman found lifeless in a pool of blood. For Martin, this is the beginning of a race against the clock. He will have to find two lost children in the city with a killer on their heels...

Martin wakes up naked, in the middle of the night, in an apartment he doesn't know and next to a woman he doesn't know either. Two days later, the body of a woman is found in the same bed and the weapon used was stolen from Martin's place...

A young girl is sexually assaulted then murdered. Martin and his team are desperate to find the culprit, but for now they don't even know the victim's identity. They end up tracing back as far as Akim Fediche, a former villain, who, however, doesn't have the profile of a paedophile.

As the appeal gets underway for Paul Vigan, a serial killer arrested by Jeannette, a woman matching the profile of the killer's victims is found stabbed. Is he the victim of a judicial error? Convinced of Vigan's guilt, Jeannette believes he must have an accomplice.

In Paris, 7 people are murdered in a bus, including Martin's girlfriend. Off the case, Martin wants answers and his investigations lead him to believe the killer will kill again. 17-year-old Aurélien is an unassuming high-school student but a terrible secret links him to the massacre.

Marie-Laure Bélier, head of the Forensic Identification Service, is accused of murder. Despite damning proof, Martin is sure of her innocence. However, he doesn't suspect that she's the victim of an obsessive and manipulative killer.