As a furious Damien tries to figure out what his mother is up to, a clue found on Séverin's computer leads the team to the next potential victim.

Damien uncovers a secret that sends him racing back to his childhood home. Unable to shake her suspicions, Lucie digs into her husband's past.

The Mantis makes her next move, Achille finds a crucial clue linking the victims, and Damien pays a visit to his mother's psychiatrist.