Summoned back to his old stomping grounds to help investigate a bizarre crime, Capt. Martin Servaz is haunted by a case from his past.
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.
Hirtmann strikes a deal for one last visit with Diane, disturbing videotapes reveal a fourth figure in the ring, and a secret alliance comes to light.
With time running out, all sides race to uncover the identity of the fifth man. As Hirtmann's endgame becomes clear, Martin faces an agonizing choice.