As night falls on the ramparts of Saint-Malo, a man tries in vain to escape the terrifying canine shadow that pursues him along the beach. The next morning, the body of René de Kermanlec is found horribly mutilated at the gates of the city. For police officers Kassem and Vasseur, there is no doubt: the patriarch of the most powerful family in Saint-Malo has been devoured by a dog... At the same time, Gwen Garrec, a former police officer who has become a real estate agent, is terrified by the disappearance of Ronan Delalande, her ex- partner and father of her son. According to the Kermanlecs, Ronan, a passionate historian, has unfailingly loathed their family for many years... He immediately becomes the main suspect in the eyes of Vasseur. But for Gwen, something doesn't add up... She goes to ask for help from Eric Vautier, a retired gendarme with whom she had teamed up ten years earlier. He doesn't trust Vasseur either. The duo then embarks on a parallel investigation, which will lead them on the trail of dark family rivalries... Meanwhile, the dog and his master claim other victims, traumatizing the entire town...
