In Peranne, in 1995, Lidia Achour, a young anti-terrorism recruit, works alongside Jean Benefro, a gendarme haunted by the Algerian war, to investigate the violent murder of an imam.

Forced to work together, Adrien and Lidia pursue various leads that only fuel the mystery; Karen Benefro, Jean's granddaughter, is worried about her ex-girlfriend Rudy's trafficking.

In the imam's murder case, Jean suspects a group of former soldiers from the Algerian War, led by the charismatic Marquis; Lidia's investigation is halted by the commander of the Marseille BRI, who has taken over the reins of the investigation.

Lidia finds herself facing a dilemma; questioned by Adrien, Rudy gives the name of a certain Willy Crusher, to whom he sold a dog implicated in the case; having recently arrived in the small town of Peranne, Crusher becomes close to a young tracker.

The body of a former member of the Patria Nostra is found in Peranne; Lidia is having a hard time coping with the revelations surrounding the case of the imam murdered in 1995; at the time, convinced of Mehdi's innocence, she asked Jean for help.

Willy, whose real name is Nicolas, is being hunted from all sides; Lidia and Adrien delve into the Benefros' past and understand what unites Nicolas and Jean; in 1995, Lidia's investigation seems to have reached a dead end.