Halle Berry in Alexandre Aja's horror

Splat Pack veteran Alexandre Aja tries his hand at family-in-peril horror, along the lines of Quiet place franchising with Never let goBut above all, the French director manages to make us regret his amusing trashy deviations towards the pulp of B-series films, with creature features built around voracious and biting carnivorous fish (Piranhas 3D) or giant Florida alligators angered by a hurricane and flood (To crawl). Whatever their strengths and weaknesses, those films were fun, popcorn-with-teeth entertainment. Fun is banished from Aja's latest, which starts off mildly intriguing and scores a few bracing scares before running out of steam.

Part of the problem with KC Coughlin and Ryan Grassby's weak script is the laboriousness of its setup. Halle Berry plays a woman, initially identified only as Momma, who lives secluded in the woods in an old wooden family home with her non-identical preteen twin sons, Samuel (Anthony B. Jenkins) and Nolan (Percy Daggs IV). Whenever they leave the house in search of food, they must remain tethered to its foundation with thick ropes and: Never. Allow. GoThis way evil can't touch them and make them do bad things, explains the mother, many times you want to scream: “Jesus, we made it!”

This amorphous evil has apparently poisoned humanity to the point that civilization has ended, 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 voice-over and then a bunch more from Mom in menacing dinner-table 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 burdened with a lot of convoluted lore that somehow never makes it coherent.

Evil can take many forms, from the snake slithering through the mossy roots of the forest trees to the zombified humans lurking, waiting for one of their own to break free. These demons want to destroy the love inside the boys, their mother tells them. It can get inside their heads and tear them apart, making them kill each other.

One manifestation of evil that seems to particularly interest Mom is a hillbilly in a housecoat (Kathryn Kirkpatrick) who drools ink and has a tongue like a lizard, or like Gene Simmons in his Kiss heyday. The suspicion soon arises that he was once part of the family. Even the boys' deceased father (William Catlett), who wanders around the house at night while Mom sits in a rocking chair on the porch, sharpening his hunting knife, seems alive except for the huge shotgun hole in his back.

The mother is so furious after a close call caused by the boys' recklessness that she threatens them with a knife while making them repeat the nursery rhyme for the 800th time. She also has a sort of purification ritual where she locks them one at a time in the cellar to imagine the darkness taking over their world and then wishes to return to the light.

At that point the film started to fall apart due to the vagueness and repetitiveness of the plot, so it's a welcome shock of madness when Berry threatens to transform into Piper Laurie in Carrie. Sadly, it stops short of that hellfire hysteria (for now at least), sticking to a low-simmering, witchy intensity and terror that occupies Mom's every waking moment. However, a seed is planted, suggesting that her maternal devotion may be more twisted than it seems.

A harsh winter has wiped out everything edible in their greenhouse, along with most of the natural vegetation worth seeking, and the woodland animals are slow to return, steadily increasing the family's risk of starvation. A skinny squirrel, skinned and fried by its mother, seems to be their last taste of substantial food before they are reduced to eating stir-fried tree bark.

Hunger, fear, and desperation drive a wedge between the brothers as Nolan begins to doubt his mother's dire warnings and plans to set out without a rope in search of food. Since their mother is the only one who sees evil, they have always had to take her word for it. But Samuel believes her without hesitation, begging Nolan not to put them all at risk.

In his latest film, Netflix's claustrophobic sci-fi thriller OxygenAja took a setting that couldn't have been more limited and kept the scenario tense and the suspense buzzing. He's working on a bigger canvas with Never let goa three-character Southern Gothic chamber piece. But the film begins to unwind 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 over-the-top possession fit, The liberation —and the makeup team does a stellar job on all three of the main cast, hollowing out their eyes and cheeks as the malnutrition takes its toll. But there’s only so much the film can get out of “Is Mom Crazy or Telling the Truth?” before it becomes monotonous.

A surprising development just past the halfway point raises the stakes significantly, as a passing hiker (Matthew Kevin Anderson) further convinces Nolan that normal life continues out there, beyond the wooded edges of their dark fairytale world. By then, however, the film has become an inevitable “and then there was one” countdown. While Aja amps up the final stretch with plenty of fiery action, shifting perspectives, demonic visitations, and a dash of body horror, it’s dull and silly and not scary.

At the artisanal level, Never let go is refined. Aja’s longtime cinematographer, Maxime Alexandre, uses wide framing to place the characters in a dark natural setting, heavy with mystery and menace. The forest location (filming took place outside Vancouver, standing in for rural Tennessee) is dense and atmospheric. Its elemental noises and the sounds of mostly unseen animals are effectively blended with a robust, haunting score by French indie pop artist Robin Coudert, who records and composes for film as ROB.

Production designer Jeremy Stanbridge makes the house feel like a separate entity, full of secrets and lit only by candles and oil lamps. As a treat on new moon nights, Mom winds up the old-time gramophone and lets the kids sing and dance to the late 1920s country-folk song “The Big Rock Candy Mountain,” a nod to the place's long history.

Berry, who also produces through her company HalleHolly, goes all out. Deglamized almost to a savage degree and slipping in and out of a Southern drawl, she expertly blurs the lines between fiercely protective and paranoid and deranged for much of the running time. But all her conviction fails to substantiate a story that’s far more complicated than complex and a film that takes itself far more seriously than the material warrants.