Spanish photographer Francesc Boix, imprisoned in the Mauthausen-Gusen concentration camp, works in the SS Photographic Service. Between 1943 and 1945, he hides, with the help of other prisoners, thousands of negatives, with the purpose of showing the freed world the atrocities committed by the Nazis, exhaustively documented. He will be a key witness during the Nuremberg Trials.
Pep, a 13-year-old boy, is in love with a girl from his grandparents village, Sara Amat. One summer night, Sara disappears without a trace. After a few hours, Pep finds her hiding in his room. Although Pep knows that the entire town is looking for her, he agrees to her stay. Consequently, the boy will be forced to live a double life: he must lie to everyone while satisfying the Sara's demands.
