Paris police commander François Visconti (Vincent Cassel) investigates the disappearance of teenager Dany Arnault. The scruffy, alcoholic cop discovers he’s attracted to the grieving mother of the missing youth, a sailor's wife who also cares for her mentally handicapped daughter at home. While his superiors analyze the hypothesis of the boy having been radicalized by terrorists, Visconti suspects a neighbor, the strange Yann Bellaile (Romain Duris). This high school literature professor, who tutored Dany, is a little too interested in the case.