They say there’s no force in the world like a mother’s love — for better or worse. English thespian Sally Hawkins, whose many roles have included Paddington Bear’s adopted mom in the Paddington movies, puts her zany energy to a different and more unsettling use in this psychological horror drama from directors Danny and Michael Philippou, who brought us the fan favorite Talk to Me.

The deal

Seventeen-year-old Andy (Billy Barratt) would do anything to protect his spirited younger stepsister, Piper (Sora Wong), who is blind. He shields her from bullies and tells her about the things and people she can’t see, often fudging the less pleasant details. But he can’t mute the shock of the day the siblings discover their dad dead in the shower.

Andy insists on accompanying his sister to her foster placement, planning to become her guardian once he turns 18. Their new foster mom, Laura (Hawkins), is a colorful eccentric who lives in a state of creative disorder. She welcomes Piper with open arms, and the siblings soon learn she’s grieving her own blind daughter, who drowned in the backyard pool.

Laura is so effusive and loosey-goosey that even Andy lets down his guard. But then he notices something is seriously wrong with her other foster child, the seemingly mute Oliver (Jonah Wren Phillips). And Laura doesn’t seem particularly perturbed.

What Andy doesn’t see, and we do, is that Laura obsessively rewatches a grainy VHS tape depicting a murderous ritual. Its purpose? To raise the dead.

Will you like it?

To people who don’t like the genre, all horror movies may seem equally nihilistic. But if you do like it, you probably recognize a vital distinction between horror that provokes screams of glee more than terror (Final Destination: Bloodlines, say) and horror that evokes existential despair.

The talented Philippou brothers, who got their start on YouTube, are purveyors of the latter. Talk to Me, a clever modern twist on “The Monkey’s Paw” with a protagonist who spirals into supernatural addiction, was unrelentingly grim even for me.

Bring Her Back shares that film’s central motifs of protective guardianship, unresolved grief and mounting delusion. But this time, the Philippous have made the savvy choice to divide those traits between two central characters, one of whom is easy to root for.

Once Andy discovers that their foster mom doesn’t plan to let Piper go, his conflict with Laura propels the story. As Laura’s tactics escalate — drugging, gaslighting, playing the siblings against each other — Andy’s touching and believable bond with Piper keeps us on his side, even when his grip on sanity falters.

We watch in horror, but it’s mixed with pity, because the film’s drifting point of view brings us into Laura’s secret world, too. The bizarre title character of last summer’s Longlegs was more meme than man, not real enough to be scary. By contrast, we’ve all known women like Laura, whose too-muchness teeters on the brink between endearing and appalling. And Hawkins’ unhinged performance connects us directly to her outsize emotions.

If watching this movie feels like bathing in a tub stained with decades’ worth of untraceable filth, that’s not because of anything supernatural. We never learn the details of the ritual depicted in the videotape; no paranormal “experts” pop up to offer exposition. This vagueness allows viewers to fill in the story’s gaps with their own conspiratorial theories — and many have. But the real dread sets in with the realization that it doesn’t actually matter whether the ritual works, only that Laura thinks it will.

She’s a cult of one, ruling over an airless house of madness, and the Philippous use all sorts of disorienting techniques to trap us there with the siblings. Ominous circular motifs repeat throughout the film, penning the kids inside Laura’s domain. Some shots are in extreme shallow focus, putting us in Piper’s place as she navigates a world seen only as light and shadow. Sound often deceives us, too, as voices issue from the wrong mouth.

To call Bring Her Back a downer would be an understatement. Be forewarned: The movie depicts harm to children and animals — more graphic in the former case than in the latter. Phillips, as the mysteriously afflicted Oliver, gives a harrowing performance in scenes that provoke the most primal of cringes.

But the siblings are likable, and Hawkins’ larger-than-life presence contributes continual jolts of energy, much like Toni Collette’s turn in Hereditary. Imagine visiting the quirky home of a creative type — a taxidermied dog! a chicken coop! — and gradually realizing their interests run deeper and darker than you ever imagined. The ritual may be demonic, but the horror here is all human.