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For children, it’s not a matter of debate: Monsters are real. As adults, we forget this, burying the truth under blankets of logic and proclamations of moral relativism. Custody, a terrifying French domestic drama, follows in the tradition of great films about divorce such as Kramer vs. Kramer and the underseen What Maisie Knew, but while those films ultimately refused to fully condemn its badly behaving adults, Custody knows a monster when it sees one.

The film starts, as most great arguments do, by acknowledging the very point it ultimately refutes. Miriam (Léa Drucker) and Antoine Besson (Denis Ménochet) sit before a judge, each of them making their case for custody. Miriam has accused Antoine of physical abuse, which her teenage daughter and younger son have corroborated. Antoine disputes it so calmly and reasonably, we leave the scene thinking that there may be two sides to every story after all.

The judge agrees, granting Antoine joint custody, and we never see him so calm again. Over the course of the next several days, he will unravel in increasingly terrifying ways. First, there’s the subtle pressure he places on his son Julien. Writer/director Xavier Legrand films several scenes of the father and son in the car in long, still shots, with Antoine slowly trying to turn him against his mother. Julien (Thomas Gioria), not yet a teeanger but old enough to know that he is being used, heartbreakingly tries not to crack under the pressure of trying to placate one parent without betraying the other. Tense and tender, he gives one of the great child performances in recent film history.

It’s hard to know just how dangerous Antoine is, due to Ménochet’s slow-burn performance. Yes, he screams and yells, but he’s even more terrifying when he is still, watching TV or driving with dead eyes, like a predator just before the kill. Legrand makes space like this for all of his actors to shine; Léa Drucker offers a study in quiet strength as a woman who is nearly consumed by a fear she cannot let her children see. As the teenage Josephine, Mathilde Auneveux is mostly absent until the final act, when all parties come together at Josephine’s 18th birthday party, and Auneveux steals the show with an unexpectedly poignant musical performance.

It’s a gripping, difficult story that induces some serious claustrophobia. We are stuck with this abusive man, much like his family members. Still, despite (or perhaps because of ) how disciplined Legrand’s narrow gaze is, the pain of the Besson family ripples outward. Consider its legacy in the canon of French cinema. One cannot hear the name Antoine without thinking of Truffaut’s The 400 Blows and the childhood hero Antoine Doinel that Truffaut revisited in several later films. He is perhaps the most iconic character in French cinema. If this Antoine is meant to be a French everyman, Custody is painting a tragic and disturbing portrait of contemporary life.

Why shouldn’t it? The existence of monsters is a subject that has received vigorous debate in our age. As our society gets increasingly polarized, some are tempted to explain away immoral and offensive behavior through an over-reliance on empathy. Look at it from his perspective, they might say, or walk a mile in her shoes. Custody both affirms and corrects this notion, demonstrating with skill and insight that even when there are two sides to every story, one might still be told by a monster.

Custody opens Friday at Landmark E Street Cinema.