A newly emerged photo of her missing son awakens new hope in Sophie Cross. She also receives support from her husband Thomas Leclercq, who, through new evidence, sets out with Sophie to find Arthur, who disappeared more than three years ago. Sophie also gets unexpected support from her superior Gabriel Deville, who advises her face to face: Never give up. The chief investigator, however, gets himself at the center of official investigations. After the murder of a private detective, the murder weapon caused a stir: the same pistol was used in a robbery five years ago.