A car drives into the forest with two scared girls trapped in the boot. The day after, Florence Grangeon reports the disappearance of Laura and Juliette Sorin, her 5 and 8 year old daughters, to the DIPJ in Lille. She and their father, Franck Sorin, had joint custody of the girls and he apparently is also missing. Arnaud, the grandfather and wealthy owner of a luxury hotel chain, considers Franck a marginal follower of collapsology theories, trying to live on a eco-responsible farm. He is the ideal suspect in their probable kidnapping for his father-in-law.

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.