Maybe “Never Let Go” looked good on paper.

Take your typical self-isolated “keep the kids safe from the world” thriller, people afraid of societal breakdown, the zombie apocalypse or an outbreak of “evil,” and jump to the part where we start to wonder if the protectors aren’t paranoid and off their rocker, and hurdle past it to see what awful things lie beyond for those raised in fear and sure of the limits of their “world” when they’re forced to confront it.

That’s like M. Night Shyamalan’s “Twilight Zone” ish “The Village,” and several other “because Dad/Mom/The Captain said so” stories with that “What’re we afraid of?” twist.

But even though this thriller has Alejandre Aja (“High Tension” was his best) behind the camera and Oscar winner Halle Berry in front of it, with its big conceit borrowed (Coincidence?) from an indie drama a few years back — “Tethered” — “Never Let Go” drifts from barely interesting to less interesting to a cop-out ending without making the viewer so much as break a sweat.

Berry’s the protective mother who guards her little boys Sam (Anthony B. Jenkins) and Nolan (Percy Daggs VI) and drills in them the rituals of their safety from the “evil” that stalks them and brought the outside world, she says, to ruin.

The youngest narrates that they’re in grandpa’s house, and it has magical powers. There’s an incantation they recite whenever they go outside.

“Oh blessed house of ancient wood, shelter to the pure and good,” it begins. They know it by heatd. There are prayers and spells carved into the doorjamb of this rustic cabin deep in the woods, and a root cellar door with ornate carvings grandpa gave it.

Something happened to grandpa. Something happened to grandma. Something happened to their dad (William Catlett), too. They see visions of them sometimes, when they’re sleeping, when they’re wandering the woods hunting rabbits and squirrels by crossbow and slingshot and harvesting slugs and popping live frogs in their mouthes for the protein.

Mom makes them wear a rope around their waists to keep them connected to the evil-repelling righteousness of grandpa’s “house of ancient wood” so that no harm will come from them from the zombies and other threats implicit in this “evil” threat Mom describes.

We have just enough time to wonder if Koda their faithful dog knows what’s up regarding those “something happeneds” when we and he get an answer, he flees and events turn dire and even more paranoid.

“There’s nobody else out there, baby,” Mom purrs, trying to keep them in line.

Because whatever happened out in the world, they’re starving to death. Listening to a 78rpm disc of
“Big Rock Candy Mountains” every time the moon is full won’t sustain them.

The brothers question each other, and they start to question their mom. And as they do, the screenplay seems to lose its point or back away from ever having had one.

“Never Let Go” is one of those movies that someone felt compelled to break into “chapters” with titles stating the obvious — “How Will I Feed My Children?”

The setting has possibilities, seeing as how 673 other horror tales have clung to a “cabin in the woods.” Berry generally gives fair value in thrillers, even supernatural ones. Not so much here.

But the sibling relationship is what resonates here, more than Mom’s paranoia or the monstrous visions or “real” manifestations the kids cope with. They bicker, collaborate and differ on what they think might really be going on here.

Is this a parable about the limits of blind faith, or the importance of clinging to it? It’s hard to tell because I’m not sure screenwriters made up their minds about that, especially after (just guessing) they were told to tag this thing with a clunky “Wait, what WERE we just looking at?” cop-out finale.

Rating: R, graphic violence

Cast: Halle Berry, Anthony B. Jenkins, Percy Daggs IV

Credits: Directed by Alejandre Aja, scripted by KC Coughlin and Ryan Grassby. A Lionsgate release.

Running time: 1:41