During a school research trip to Buchenwald concentration camp, young French teacher Nathan Fabre (Stanley Weber) discovers a photograph of a prisoner whose resemblance to his own father, Adrien (Richard Berry), is uncanny. Driven to investigate his family's past, Nathan uncovers a buried history: the prisoner in the photograph, David Wagner (César Chouraqui), was a Jewish man who had a covert affair with Nathan's grandmother during WWII. As Nathan digs deeper into the betrayal that led to David's deportation, he uncovers a web of familial silence, anti-Semitic denunciation, and illicit passion that reshapes his entire lineage.