While walking his dog, someone tries to kill Emilien Kerr, 62, by suffocating him with a plastic bag, but the concierge of his apartment finds him in the parking lot and the emergency services keep him alive although he stays in a deep coma. Kerr was a widower, a loner who worked as German translator, leading a calm life, but Alvaro finds that he had been set up. Apparently he had had dinner with his daughter Alexia, 29, ten years after his wife's suicide, of which she accused him. Alexia becomes main suspect, while another daughter visits Emilien in the hospital.

The body of Axel Maertens, 32, sailing and kitesurfing instructor and manager of the nautical club at Malo-les-Bains, is found suffocated with a rope on a beach, presumably by accident. Morgane notices that the knot was not tied by a sailor, such as Axel, which means it was a murder. A certain Jonathan, who at first declared to have witnessed the murder, finally confesses that he committed the crime, a situation that makes everyone feel relieved, but that Morgane and Karadec find hard to believe. They join forces to continue with the investigation.