And with his career hanging by a thread - his resignation letter parked in his superior's desk draw - he is plunged into his most testing ordeal yet.
A raid on the vault at the Bobigny law courts. Five vital pieces of evidence swiped. Four men who can no longer be held: an armed robber, a foreign legionnaire, a kidnapper and a paedophile.
But what is the connection between them?
With Coste and his team at a loss, it's the moral outrage of another criminal that will throw up a lead: one they'll follow to their breaking point - and beyond.
