While investigating the roundup and deportation of more than 13,000 Jews in occupied Paris in 1942, American-born journalist Julia Jarmond (Kristin Scott Thomas) uncovers the story of a girl who lived in the apartment in the Marais where Julia's husband grew up. To save her little brother, 10-year-old Sarah (Mélusine Mayance), locked him in a hidden closet in the apartment, but then was unceremoniously shuttled off to the Vélodrome d’Hiver, where in cramped and unsanitary conditions, she and her mother and father were forced to wait for days for transport to a prison camp outside of Paris, where they were then separated, and her mother and father shipped off to Nazi concentration camps outside of France.
In a desperate attempt to free her brother from the closet, Sarah escaped the camp and found refuge with a rural Christian family. However, a risky return to Paris proved Sarah was too late. Although Julia's in-laws played no part in Sarah's family's deportation, Julia becomes obsessed with the story, eventually leaving her own family to make contact with Sarah's adopted family and to track Sarah's life as a young woman.
In Gilles Paquet-Brenner’s Sarah's Key, the historical scenes drive the story forward, propelling it toward a sad and powerful conclusion. Mayance's performance is nuanced. Sarah is wide-eyed and frantic, yet still wise beyond her years. Especially during the scenes of intense horror, Sarah is sympathetic and even charming. As her parents blame her for her brother's separation from them, her face sets in an expression of fear and determination. Sarah's obsession with the girl, then, is understandable. However, the modern-day frame story, burdened with the coincidental connection between Sarah and Julia — whose father-in-law remembers Sarah's return to the apartment's hidden closet — slows the story down and removes Sarah as the focus of the film. In comparison to Sarah's uprooted life, Julia's troubles seem petty and uninteresting. Also, despite Scott Thomas' bright performance, Julia's righteous manner is off-putting. Her lectures on culpability and apathy come straight from the “tell, don't show” side of storytelling used most often for when the subject matter trumps technique.
Director Gilles Paquet-Brenner, who also wrote the screenplay with Serge Joncour, focuses not on Sarah's later life, but on Julia's research of Sarah's later life. To take the most interesting character in the film and make an audience care for her, and then let the rest of her story be told in summary is a cruel mistake. Not even Julia's ultimate tribute to Sarah, naming her daughter after her, can make up for that.