Child killer Guy Béranger is released after 20 years in jail. He seeks refuge with the monks of Vielsart, a small village in the Ardennes, and is placed under the protection of a federal police inspector. A few days later, a little girl goes missing.

The case takes a new turn when the autopsy reveals a symbol carved into the little girl's scalp: it's Béranger's infamous signature. At the abbey, whilst Lucas' efforts to integrate Béranger into the community begin to bear fruit, the new suspicions weighed against the ex-criminal cast doubts on his place amongst them. Is it possible to trust a child-killer? Although everyone around her seems persuaded that Béranger has relapsed, Chloé's investigations lean in favour of his innocence. Is there a copycat at work, someone trying to imitate Béranger's crimes?

Lucas sends Béranger to Brother William to test his convictions. Chloé and Michaël scour Béranger's past, hoping to find someone likely to reproduce his crimes. They discover that while in prison, the famous murderer maintained a passionate correspondence with an admirer, Sarah Decoster, the criminal's biggest 'fan'. When they learn that she also tried to contact her idol at Vielsart, they decide to use Béranger to lure in the young woman.

Chloé is forced to accompany Béranger on a visit to his dying mother.

Vincent and his gang are in hot pursuit after Béranger, and succeed in getting their hands on the ex-criminal. Chloé has no other choice than to assemble a team, this time with both of the Stassart brothers (Lucas and Patrick), the only two capable of tracking Vincent across the immensity of Vielsart forest. The unlikely trio is in a race against time: they must find Béranger before Vincent and his gang take justice into their own hands. For Michaël things get complicated when it seems that a new child (Laurent) has gone missing in Vielsart.

Chloé is cornered by Béranger, who reveals that he knows the identity of the Toy Dealer, the man who held her prisoner. In exchange for information, Béranger offers to make a pact with Chloé, which would force her to lie to the people closest to her. Sarah's father offers a deal to Patrick: he will finance the entire brewery project in exchange for Béranger's life. At the Vielsart police bureau, Michaël makes a major discovery in the investigation when he stumbles upon a video that Laurent made the night of Noémie's murder.

Chloé and Michaël are called to investigate a strange incident at the abbey. After assaulting a monk in the sacristy, a mysterious stranger seems to have fled into a centuries-old underground tunnel. What if Béranger knew about this tunnel since the very beginning?

Little Bastien manages to escape his aggressor but falls into a deep coma. While digging through the archives, Chloé comes across a name: Lucas Stassart. The young monk reveals some hard-to-swallow truths about his troubled past to the investigators and in the end gives up the identity of the mask's last-known owner.

Commissioner Gomaz accuses Chloé of acting alone and calls her entire investigation into question: what if she's been manipulated by Béranger since the start? Suspecting that Chloé is mentally fragile, he suspends her from her functions. With the investigation shattered, Michaël comes across a final clue

Chloé is granted a reprieve to finish her investigations. She manages to retrace the final elements all the way to Judith, and comes across Michaël who has been left for dead. At the abbey for All Saints Day mass, Patrick takes the monks into hostage. On the other side of Belgium, the story takes a new turn when we learn that the Toy Dealer is still active and at large.