Jean Firmino (Guillaume Gallienne), the respected director of a women's detention center, leads a quiet and predictable life with his wife and family. Everything changes when a new young inmate, Anna Amari (Adèle Exarchopoulos), arrives at the prison. Drawn to her free spirit and vulnerability, Jean gradually initiates a secret, highly forbidden romantic and physical affair with Anna inside the facility. As their passionate connection deepens, Jean risks his marriage, career, and freedom as the boundary between authority and obsession completely collapses.