After visiting the prison, Martin realizes the horse may be part of a more sinister scheme. Diane's first session with Hirtmann proves unsettling.

A body found in the woods leads the detectives to re-examine an old case that hits close to home for Irène. Martin follows a clue back to Toulouse.

While Martin turns his attention to Alice's family, Irène goes rogue to investigate another friend of Perrot's. A prison brawl puts Diane in danger.