In the small town of Fermont, Celine and Alexandre must solve the murder of a woman who was found inside the city's "wall," wearing a Chinese mask.

Celine and Alexandre make progress with the investigation; they learn that on the night she disappeared, Justine left the bar with a mysterious man.

A new disappearance worries the police and Dave doesn't show up for work; the fleeing duo is caught, and Anthony makes troubling confessions.

Celine and Alex uncover the identity of a man; a new corpse is discovered; Celine figures out who the killer is.

Celine sees the pattern behind the murders: the victim, the executioner, and the matriarch behind it all. She soon realises her daughter is in danger.