New Zealand author Margaret Mahy’s well-received 1984 YA novel serves as the basis for this adaptation by Miranda Harcourt and Stuart McKenzie, which brings a moody, hallucinatory cast to its story of a girl with second sight who must embrace her destiny as a full-fledged witch in order to save her little brother from possession by a demonic creature that feasts on the life-force of children to remain immortal.

The teen protagonist, Laura Chant, is played, quite well, by Erana James: she’s a girl with the power to intuit bad things before they happen. Having survived a recent earthquake in her hometown of Christchurch in which her father died, she’s extraordinarily protective of her brother Jacko (Benji Purchase), especially since her mother Kate (Melanie Lynskey) remains traumatized by the national—and familial—tragedy.

She’s approached by Sorenson Carlisle (Nicholas Galitzine), a handsome but diffident schoolmate who tries to warn her that she’s in danger, but blows him off. Unfortunately, it’s an admonition she should have taken seriously. Soon after Jacko is approached by Carmody Braque (Timothy Spall), a friendly but off-putting fellow who’s opening a fly-by-night antique shop in a cramped storage shed. Suspicious Laura tries to pry her brother away, but before they can leave Braque genially stamps the boy’s hand with an image of himself—an act that, as Laura later learns, begins the takeover process.

As Jacko becomes more and more listless, winding up in the hospital and in need of an operation to survive, Laura turns to Sorenson, who’s able to explain what’s happening. His inability to help on his own leads him to introduce Laura to his mother Miryam (Lucy Lawless) and grandmother Winter (Kate Harcourt), who can show her the way to embrace her destiny, confront Braque and liberate the victims he’s accumulated over the centuries. Whether she can save Jacko, however, remains in doubt to the very end.

Harcourt and McKenzie, along with cinematographer Andrew Stroud and editor Dan Kircher, cultivate a woozy, off-center style in “The Changeover”—a title with a double meaning, referring to both Jacko and Laura—that is bound to disorient many viewers; the final reel, in particular, goes on a journey that seems almost chaotic, and concludes with a literal miracle that, one would imagine, would attract far more public attention than is the case here.

On the other hand, the cast is excellent. James makes a feisty heroine—more determined Katniss Everdeen than whimpering Bella Swan—and though handsome, Galitzine’s Sorensen never grabs center stage the way Robert Pattinson’s Edward Cullen did. The others—Linskey, Lawless, Harcourt, little Purchase—all play things straight, refusing to wink at the audience as the story unfolds.

The ace in the deck, though, is Spall. The modestly-budgeted movie is hardly awash in special effects, but with him, they’re hardly needed. To be sure, his closing transformation involves some creepy imagery, but up until that point, apart from some light youth-enhancing makeup and a skillful blending of separate lines of dialogue turning on and echoing one another (kudos to the sound design team headed by Melanie Graham), he makes his frightening impression through quite direct means. Other films have demonstrated his ability to exude malice, but none has put his smarmy, sinister side to better, more unsettling use.

Without Spall, this would be intriguing but dispensable; he single-handedly raises it to the level of an effective teen thriller, imperfect but nonetheless worth a look.