A young girl is found dead in 1998 Perpignan. A connection emerges with a past disappearance. Called in by the police commissioner and having never been a member of a crime team, Detective Flore Robin bravely assesses the crime scene and vows to hunt down the killer.

As the investigation into Leïla's murder intensifies, Vidal's team focuses their efforts on Olivio Palomyno, a doctor exhibiting strange behaviour; during their surveillance of the suspect, the officers uncover increasingly disturbing clues.

Palomyno is held and interrogated as the prime suspect in Leïla's murder; while he has been the main lead for months, the investigation takes a turn when another young woman disappears under troubling circumstances.

As the world prepares to enter the 21st century, the investigation stalls, plunging the team into doubt; to assist them, a controversial profiler is sent from Paris, whose extravagant theories complicate the investigators' work even further.

The investigators race against time to apprehend a new suspect. However, his confessions raise more questions than answers. Nora's body is found, but the investigation remains mired in uncertainties about the other victims.

After sixteen years' on the run, the perpetrator of two of the murders is caught, thanks to a DNA match. During an interrogation, Flore, with Vidal's help, forces the suspect to confess to murdering Leïla and Marianne.