Sarah's Key tells the story of Julia (Kristin Scott Thomas), an American expat journalist in Paris who discovers that the apartment she's about to move into has a deeply unsettling connection to the past. While researching a story about the Vel' d'Hiv roundup of Jews in Paris, conducted by French police in 1942, Julia becomes obsessed with tracing what happened to one victim in particular, a 10-year-old named Sarah.
Sarah's Key intercuts Julia's story with Sarah's until those stories inevitably intersect in the present day. Director Gilles Paquet-Brenner, working from a novel by Tatiana de Rosnay, employs a careful tone, which is sensible when he's following the upstanding reporter on her research. As Julia tries to track down Parisians old enough to have witnessed the roundup, she treads lightly and respectfully, and the film follows suit. But Julia starts taking the thing personally and gets obsessive about Sarah, jeopardizing her marriage in the process. The ethical boundaries of her quest get a little thorny, and Julia gets in over her head.
But the movie doesn't keep pace. The restrained rhythm and photography, and the just-so lighting, start to feel too polite, and the film seems to be trying to apologize for Julia's obsession or (worse) doesn't recognize it. Something more fevered is called for here, not only with Julia's narrative but with Sarah's. On paper, Sarah's story is a historical allegory telescoped into a disturbing gothic tale (her brother is stuck in a hidden closet!), but Paquet-Brenner reduces it to an unsurprising history lesson drawn from the life of a headstrong, overly sophisticated 10-year-old. Not every story about a girl who loses her family in the Holocaust has to be as nutty as Inglourious Basterds, but the disparity between the content of the story in Sarah's Key and the frustrating, quaint way it's told is a unsatisfying missed opportunity.