When the body of a young woman is found murdered and mutilated, police captain Laure Berthaud seizes the opportunity to redeem a tarnished reputation and leads her squad on the hunt for the sadistic killer. Meanwhile, Judge Roban's investigation into the case of a child being bitten by a dog might turn out to have broader implications, and even public prosecutor Pierre Clement is not immune from the resulting pressure.

With the second body identified as that of missing girl Celia Morau, police believe that they could be looking for a serial killer and delve into the unsavoury depths of the Paris underworld in their search for clues. The pressure piles on, with Judge Roban threatening to hand the case over to the Serious Crime Squad in the absence of prompt results, and Captain Laure Berthaud is on the brink of mental instability when an important breakthrough occurs.

Judge Roban betrays a surprising side to his character when an old flame gets in touch, barrister Josephine Karlsson moves to disassociate herself from Szabo and an unlikely alliance might be in the offing for former public prosecutor Pierre Clement.