Time Out says
For a change, let's not debate the Holocaust-movie glut now that we're being sold another take on the subject and simply say this: When Sarah's Key leans into the horror (as it should), it's harrowing. Alas, that's only half the time. Keenly adapted from Tatiana de Rosnay's 2007 best-seller, Gilles Paquet-Brenner's film has a coup in young Mlusine Mayance, magnetic as the ten-year-old title character shuttled through France's ignominious Vel' d'Hiv, an athletic stadium where thousands of Jews were rounded up in 1942 and sent to camps. This sequence---confused people screaming in the sweltering stands and plunging to their suicide---is a key dramatization, sure to counter many American impressions of French resistance.
Sarah escapes the holding site of Beaune-la-Rolande, makes it back to her family's occupied Paris apartment and encounters even more personal shock (expertly rendered in a suggestive way). But since this is also an awakening story, we're made to endure Kristin Scott Thomas's unpersuasive hand-wringing as a modern-day journalist tracking down the history of her flat. Undoubtedly it's a crucial component of the novel's impact, lefty guilt ringing hollow compared to real sacrifice. But that's still no reason to foist a mewling Aidan Quinn on us, playing an unwitting beneficiary of a girl's courage.
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