The first is that of ten-year-old Sarah Starzynski, a Jewish girl born in Paris, who is arrested with her parents during the Vel' d'Hiv Roundup.

The second plot follows Julia Jarmond, an American journalist living in Paris, who is asked to write an article in honour of the 60th anniversary of the roundup.

On 16 July 1942, French police raided the Starzynski apartment in Paris, arresting ten-year-old Sarah and her parents.

Sarah, now on her own, is still tormented by thoughts of her brother locked in the secret closet at home, and tries to escape with Rachel, another Jewish girl at the camp.

The girls find refuge with an elderly couple who takes them into their house, but Rachel falls ill with what is probably diphtheria or typhus fever.

Jules and Geneviève dress Sarah in boy's clothes (her hair had been cut short at Drancy) and help her get to her former home in Paris.

She was born in Boston, Massachusetts but moved to Paris in her early twenties and married a Frenchman named Bertrand Tezac and had a daughter, Zoë.

She does a little more research and becomes in touch with descendants of Jules and Geneviève and they tell her that Sarah had continued to live with the family into her teens, but she grew up an introverted, sad young woman.

Weeks later, the same night Bertrand's grandmother has a stroke, William shows up in France, finally ready to hear Sarah's story.

William, having uprooted his own life too in the wake of everything he has learned about his mother, also moves to New York City and eventually tracks down Julia again.

It is revealed that Sarah did not merely die from a car accident as previously believed, but had killed herself intentionally, unable to bear with the pain of her secret past any longer.