At once beautifully realized and brutally uncompromising, “Our Children” opens with a woman weeping. She’s a lovely young thing, her features almost obscured by the grayness of her skin, the puffiness around her eyes and the oxygen tubes threaded into her nose.

“You’ll bury them in Morocco,” she says to someone hovering nearby and then, as her tears begin to fall, she repeats her appeal. The intensity of the plea is a tug at the heart, a tug that turns into a jolt with a blunt cut to four little coffins being loaded on a plane.

The reason for her weeping seems unambiguous, but the story that Belgian director Joachim Lafosse tells turns out to be anything but obvious. After its shocker opening, the movie effectively begins anew, this time with a cut to the young woman, Murielle (Émilie Dequenne), moaning in ecstasy. She’s in the embrace of her lover, Mounir (Tahar Rahim). Youth radiates from the couple.

After a few preliminaries, Murielle weds Mounir, moving into the house he has long shared with an older, well-established doctor, André Pinget (Niels Arestrup). An enigmatic figure whose mysteries peel away slowly, André scarcely seems interested in Murielle even when she eagerly tries to impress him. Her anxiety is understandable; he’s something of a father figure to Mounir. For years, André has been taking care of Mounir and his relatives, both with money and immigration help, which might register as altruistic if Mounir didn’t seem so anxious and André so controlling.

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If Murielle doesn’t seem to mind, it’s partly because she doesn’t have much of a family and, like Mounir, she very much wants to please André.

Time passes and everyone gets along amid the children’s shrieks and cluttered toys, but the rooms start to shrink, as does Murielle’s smile. The men become snappish, demanding.

There’s no denying how tough it can be to watch a family melodrama mutate into a horror movie. But the performers go a long way to keeping you tethered, particularly Dequenne.