Although you might figure out the big final twist in “Goodnight Mommy” early on—which isn’t all that difficult to do, even if you haven’t seen Robert Mulligan’s 1972 adaptation of Thomas Tryon’s “The Other” to serve as a prompt—it will probably still fascinate you, as well as creep you out. When considered alongside the films of Michael Haneke and the novels of Thomas Bernhard—not to mention the recent Blu-ray issue of Gerald Kargl’s 1983 “Angst”—the thriller by Veronika Franz and Severin Fiala suggests that there’s something very odd going on in the Austrian psyche.

The narrative line in the film is absurdly simple. After alluding to the notion of the “perfect” family with a shot of the Von Trapps singing a lullaby in harmony, the film introduces adolescent twin brothers Elias and Lukas (Elias and Lukas Schwarz) having a game of tag in a cornfield near their starkly furnished modernist home. It’s situated in a rustic area where the boys also have access to a lake, forests and farmland. But they appear to be getting by on their own until their mother (Susanne Wuest) returns, her face swathed in bandages. Though the cause of her condition is initially unclear, it gradually appears that she’s a television personality who’s undergone cosmetic surgery to preserve her youthful look for the camera.

But the twins are suspicious. Their mother, it seems, has changed more than her face. Her personality is different as well—no longer the sweet, loving parent she once was, she spends most of her time resting in bed, demanding quiet and darkened rooms. And she makes a point of ignoring Elias. Most suggestively, while playing a game with the boys she fails to identify the person they’ve chosen for her to pretend to be—their mother. And so they come to believe that under the bandages she might be someone else. And since their father is absent—all the photos of him have been systematically pruned from the family scrapbooks—they can’t discuss their suspicions with him. Those same scrapbooks do contain, however, photos in which their mother appears with a woman who looks very much like her: could a malign switch have occurred?

Not that the twins seem particularly normal themselves. Although they show signs of compassion when they hide a stray cat in their room, they generally play ferociously, jumping frantically on a trampoline and hurling hailstones at one another. They collect large, ugly beetles in an aquarium. They trample inside a tomb filled with bones and skulls that can’t help but call the Holocaust to mind. And after an attempt to enlist the local priest in their concerns about their mother fails, they determine to take action themselves, using all means necessary to get the woman upstairs to prove she’s their mother or admit she’s not.

“Goodnight Mommy” gets quite gruesome at this juncture, but amidst the gore it has its share of nicely sustained suspense moments—most notably a visit by a couple of folks going door-to-door seeking Red Cross contributions—and however nasty the action becomes, it’s all filmed in lustrous widescreen 35mm (as emphasized in the closing credits) by cinematographer Martin Gschlacht and cannily edited by Michael Palm.

The casting is also spot-on. The Schwarz twins seem normal on the surface, but they can suddenly turn sneaky and threatening. And Wuest manages to seem oddly sinister even with that bandaged face (think of Claude Rains in “The Invisible Man”) before becoming the target of the boys’ grim questioning. Together the three fashion a portrait of an attenuated family that goes far past conventional eccentricity; every one of them is a bit off from the start, and by the end all have become positively unhinged.

Unlike most of today’s cookie-cutter horror movies, “Goodnight Mommy” is a genuinely unsettling tale of domestic dysfunction grounded in natural, though unquestionably exaggerated, causes. Its big plot twist may not be all that surprising, but its coolly unnerving approach is certainly disturbing. It may even give you second thoughts about taking that vacation to Austria.