Halle Berry in Alexandre Aja Horror

Splat Pack veteran Alexandre Aja tries his hand at family-in-peril horror along the lines of the Quiet Place franchise with Never Let Go. But mostly, the French director just succeeds in making us miss his entertainingly trashy swerves into B-movie pulp, with creature features built around ravenously bitey carnivorous fish (Piranha 3D) or giant Florida gators riled up by a hurricane and flood (Crawl). Whatever their strengths and weaknesses, those movies were fun popcorn entertainment with teeth. Fun is banished from Aja’s latest, which starts out mildly intriguing and chalks up a few bracing jump scares before running out of juice.

Part of the problem with KC Coughlin and Ryan Grassby’s feeble screenplay is the laboriousness of its setup. Halle Berry plays a woman, initially identified only as Momma, living in woodlands isolation in an old timber family home with her preteen nonidentical twin sons, Samuel (Anthony B. Jenkins) and Nolan (Percy Daggs IV). Whenever they step outside the house in search of food, they must remain tied to its foundations with thick ropes and: Never. Let. Go. That way evil can’t touch them and make them do bad things, explains Momma, so many times you want to scream, “Jesus, we get it!”

This amorphous evil apparently has so poisoned humanity that civilization is over, and only the warmth and love of a house built by the boys’ grandfather as a refuge for his fearful wife can keep them safe. We get a dose of this setup from Nolan in voiceover and then a bunch more from Momma in ominous dinnertime stories and warnings both patiently nurturing and enraged. There’s even a rhyming incantation they recite before venturing out and another for once they’re back inside, their hands touching the sacred wood. The premise is encumbered with a lot of convoluted lore that somehow never makes it more coherent.

The evil can take many forms, from the snake that slithers around the forest’s mossy tree roots to the zombified humans lurking in wait for one of them to become untethered. These demons want to destroy the love inside the boys, Momma tells them. It can get inside their heads and divide them, driving them to kill one another.

One manifestation of evil that appears especially interested in Momma is a hillbilly in a housedress (Kathryn Kirkpatrick) who drools ink and has a tongue like a lizard — or like Gene Simmons in his Kiss heyday. The suspicion arises early on that she was once part of the family. Also circling the house at night while Momma sits in a rocker on the porch, sharpening her hunting knife, is the boys’ late father (William Catlett), who looks alive aside from the huge shotgun hole in his back.

Momma is so furious after a close call caused by the boys’ recklessness that she threatens them at knifepoint while making them repeat the rhyme for the 800th time. She also has a kind of purification ritual where she shuts one of them at a time in the cellar to imagine the darkness taking over their world and then will themselves to come back into the light.

The movie has started to fall apart by that point due to the vagueness and repetitiveness of its plotting, so it’s a welcome shot of craziness when Berry threatens to go full Piper Laurie in Carrie. Sadly, she stops short of that hellfire hysteria (at least for now), sticking to a low-boil witchy intensity and a dread that occupies Momma’s every waking moment. Still, a seed is planted, hinting that her maternal devotion may be more twisted than it seems.

A harsh winter has killed off anything edible in their greenhouse, along with most of the natural vegetation worth foraging, and the woodland animals are slow to return, steadily increasing the family’s risk of starvation. A scrawny squirrel, skinned and fried up by Momma, seems to be their last taste of substantial food before they’re reduced to eating sautéed tree bark.

Hunger, fear and desperation drive a wedge between the brothers when Nolan begins to doubt his mother’s dire warnings and plots to set out ropeless in search of food. Since Momma is the only one who ever sees the evil, they have always had to take her word for it. But Samuel believes her unquestioningly, begging Nolan not to put them all at risk.

In his last film, the claustrophobic Netflix sci-fi survival thriller Oxygen, Aja took a setup that could not have been more confined and kept the scenario taut and the suspense humming. He’s working on a larger canvas with Never Let Go, a three-character Southern Gothic chamber piece. But the movie starts slackening almost as soon as we digest all of Momma’s teachings.

The friction between the brothers is well-played by the two terrific young actors — Jenkins has shouldered more than his fair share of evil lately, after Lee Daniels’ inadvertently campy possession freakout, The Deliverance — and the makeup team does excellent work on all three members of the principal cast, hollowing out their eyes and cheeks as malnutrition takes its toll. But there’s only so much mileage the movie can get out of “Is Momma crazy or speaking the truth?” before it becomes monotonous.

A startling development a little over the halfway mark ups the stakes significantly and a passing hiker (Matthew Kevin Anderson) makes Nolan even more convinced that normal life carries on out there, beyond the woodland boundaries of their dark fairy-tale world. By then, however, the movie has become an inevitable “and then there was one” countdown. Even as Aja amps up the closing stretch with lots of fiery action, shifting perspectives, demonic visitations and a touch of body horror, it’s dull and silly and not scary.

On a craft level, Never Let Go is polished. Aja’s longtime cinematographer Maxime Alexandre uses wide framing to position the characters in a brooding natural setting heaving with mystery and menace. The forest location (shooting took place outside Vancouver, standing in for rural Tennessee) is dense and atmospheric. Its elemental noises and the sound of mostly unseen animals are effectively blended with a robustly eerie score by French indie pop artist Robin Coudert, who records and composes for film as ROB.

Production designer Jeremy Stanbridge makes the house its own kind of entity, full of secrets and lit only with candles and oil lamps. As a treat on new moon nights, Momma winds up the old-timey gramophone and lets the boys sing and dance to the late-1920s country-folk song “The Big Rock Candy Mountain,” which indicates the place’s long history.

Berry, who’s also a producer through her HalleHolly company, gives it her all. De-glammed almost to a feral degree and slipping in and out of a Southern accent, she deftly blurs the lines separating fiercely protective from paranoid and unhinged for much of the duration. But all her conviction can’t breathe substance into a story that’s way more complicated than complex and a movie that takes itself far more seriously than the material merits.