The opening scene of Sarah’s Key is dreamy and bright. It is 16 July 1942 in Paris and 10-year-old Sarah Starzynski (Mélusine Mayance) and her younger brother, Michel (Paul Mercier), giggle and play hide and seek in the white sheets on their bed. Their innocent game quickly gives way to one with dire consequences: French authorities, emptying the Marais neighborhood of Jews in cooperation with German officials, arrive to arrest the Starzynski family and move them to the Vélodrome d’Hiver, a nearby stadium. In an effort to protect Michel, Sarah hides him in a closet and locks the door, making him promise to stay quiet until she comes back for him. Of course, she can’t know they aren’t coming back, that they and 13,000 other Jews will be held for days in the miserable conditions of the Vel d’Hiv, awaiting eventual transport to Auschwitz.

Based on Tatiana de Rosnay’s 2008 novel, Sarah’s story is revealed in flashback, intercut with an investigation conducted by Julia (Kristin Scott Thomas), a present-day journalist working on a magazine piece about the Vel d’Hiv Roundup. Julia soon finds herself tracking down what happened to the Starzynski children, a project that has far-reaching implications for her and her own family.

The film’s presentation of Sarah’s time in the Vel d’Hiv with her parents and then at the interim camp, where she is separated from them, is beyond gut-wrenching. Her attempts to escape the camp at Beaune-de-Rolande and return home to save her brother are framed by our awareness of her uncanny intelligence (indicated when she first hides Michel in the closet) as well as her naïvete. When she arrives at the stadium, she’s confused but still sure that they will be going home soon. The desperation of all the adults around her quickly brings the reality of the situation into focus and all childishness, except the hope of rescuing her brother, drains away.

Julia’s story is different: she knows at least a little of how bad the Holocaust has been. After solving the mystery of Sarah and Michel, she then launches a new investigation into the fate of post-war Sarah (Charlotte Poutrel). The contrast between the two Sarahs is extreme, unsubtly reminding us that war is hell. Sarah as an adult is little more than a ghost. Julia’s research frames images of Sarah silently staring out windows and over oceans: her later life is tragic, the film suggests, because she’s merely surviving rather than actually living.

Living involves knowing, in Sarah’s Key, and knowing has consequences. These are weirdly drawn out along gender lines. Julia is willing to pay a high personal price for the truth, while an odd collection of fathers is bent on hiding the truth about Sarah. Some of these men mean to protect themselves or their families, and some to protect Sarah. Those who knew her firsthand bury the evidence of her lock boxes, admitting they “don’t want to know” or that they are afraid to ask. Whatever the motive, the result is the same: Sarah remains locked away, a sort of repetition of her hiding Michel.

Besides being the driving force in discovering Sarah’s story, Julia serves as both the conscience of the film and the mediator between the past and present. It is clear Julia is distressed when an elderly woman who had lived across the street from the Vel d’Hiv tells her she knew what was going on there, but said and did nothing in response: “What could we do anyway?”, she asks. But when a young coworker rants about those who stood by, Julia has her own question: “How do you know what you would have done?” Whether she can muster as much understanding when she finds out her own connection to the Marais neighborhood is another question.

As Julia ponders the past, the connection between Sarah’s Key and current tensions about immigration is clear. It is not merely anti-Semitism that fuels those French shown jeering as their Jewish neighbors are hauled away, but nationalism and the anxiety over huge influxes of refugees. When warned they might be the next victims of the Nazis, one of them yells back, “We’re French. It won’t happen to us.”

Julia also brings the horror of Vel d’Hiv into a discomforting proximity to Hurricane Katrina, when she describes what she’s found in this way: “Think: the Superdome, but a million times worse.” She notes, too, the irony that the Ministry of the Interior now stands at the site where the Vel d’Hiv once stood—a reference to then Interior Minister Nicolas Sarkozy’s 2006 roundup of hundreds of illegal immigrants into a makeshift refugee camp in gym in Cachan.

Sarah’s Key stops short of saying outright that past is prologue, focusing instead on the importance of remembering and retelling our histories. Julia is warned at the start of her research, “When you start looking into this, you don’t come out unscathed.” But she comes away thinking that, regardless of the painful consequences of learning the truth, not knowing is not an option.