Lawyer Sophie Cross and her husband Thomas Leclercq look at crime with different eyes. While he is responsible for the investigation as the head of the local police, she fights as a criminal defense lawyer with all legal means for her clients - regardless of the question of guilt or justice. When their six-year-old son Arthur disappears without a trace while playing in the dunes in a brief unsupervised moment, a nightmare begins for the two of them.

The teacher Claude Lemaire was slain after a parents' evening. Sophie Cross is commissioned by chief investigator Deville to examine the victim's private life with her colleagues Amina Dequesne and Fred Fontaine.