We start in Paris in 1942 where the ten-year-old Jewish girl Sarah hides her younger brother in the wardrobe just before the family is brutally arrested by the French police in the notorious gathering of Jewish families - Vel'd'Hiv. She locks the door to the wardrobe and puts the key in her pocket, convinced she'll be back in a few hours. But the hours get on and Sarah's desperation is growing. 60 years later Julia Jarmond is asked to write an article about this black day in French history. During her search, she stumbles over Sarah's family history.