During Custody’s opening scene — a judge-mediated custody hearing between ex-spouses Miriam (Léa Drucker) and Antoine (Denis Ménochet) — the latter’s lawyer pleads with the judge to side with her client, arguing that, despite his reported history of violence and the reluctance of the couple’s 11-year-old son to live with him, “Nothing here is black and white.” Custody plays something of a poker face in its first few minutes, leaving us as reliant as the judge is on arguments like these, but outside of the mediation room, the film’s tight 93-minute runtime builds to a finish that will conclusively — and terrifyingly — prove that claim false.

The skill of Custody, however, is in the fact that we don’t need this definitive proof to form our judgment, because we can feel the silent threat of it in every preceding frame. Each of its naturalistic scenes, whether ostensibly quotidian or celebratory, is suffused with simmering dread and ticking tension; even when he’s absent, Antoine looms over the family’s life like a dark cloud. With such restrained mastery over a thriller-like tone, Custody reveals the family’s all-too-common reality as the horror it really is.

It goes without saying that Ménochet has a big part to play in crafting the film’s stewing sense of menace, but his work is magnified by everyone else’s reaction to him — in particular, by Thomas Gioria’s performance as Miriam and Antoine’s young son Julien. Director Xavier Legrand often sets the camera at Gioria's eye-level to embed us in the impossible position the courts have forced Julien into. The agonizing pressure placed on his young shoulders — to protect part of his family and assuage the rage of the rest — is horribly palpable on Gioria’s face and in the way he uses silence as a defense mechanism. To be sure, the strength and subtlety of his performance make for an intensely harrowing watch, but it’s essential to conveying the emotional reality of the subject matter.