Review: Romola Garai makes a nerve-jangling feature directing debut with the thriller ‘Amulet’

“Forward is not the only way,� a nun remarks early on in “Amulet,� sounding a bit like a character out of Lewis Carroll. As played with a chipper smile by the great Imelda Staunton, her face beaming out from under a light blue wimple, Sister Claire looks a bit like a Carroll creation too: less committed to a particular notion of good or evil than to the cultivation of her own eccentricity. If you’ve seen Staunton as Dolores Umbridge in the “Harry Potter� movies and in the title role of “Vera Drake,� you know she can do impish malevolence and saintly warmth with equal ease. Rarely, though, does she get the chance to balance the two as deliciously as she does here.

If forward is not the only way, then this zigzagging booby trap of a thriller is shrewd enough to prove it. Sister Claire isn’t the main character in this story; that would be Tomaz (Alec Secareanu), whom we first encounter as a soldier in some unspecified European country. There’s a war on, and Tomaz has been sent to a remote outpost in some misty green wilderness. Soon enough, the story will leap forward to find him living in London, but it will also keep leaping back, returning to that outpost in scenes that insistently blur the line between past and present, flashback and nightmare.

An agreeably nerve-jangling feature writing-directing debut from English actor Romola Garai, “Amulet� barrels through its hectic, harrowing plot with an intensity that can seem feverish and mechanical by turns. It starts throwing details at you almost immediately, each one building on yet also undermining the last, as if it were deliberately trying to confound your sense of what kind of movie you’re watching.

This is a refugee story, as we see from Tomaz’s routine around London, where he does construction jobs by day and sleeps in a crowded shelter by night. It’s also a tale of war and repressed trauma, as we soon gather from those woodland flashbacks, where Tomaz huddles in his lonely quarters with just a rifle and a suggestive copy of Hannah Arendt’s “On Violence� for company. And when Tomaz discovers a mysterious tchotchke — a stone figurine carved in the shape of a woman, her head crowned by a large shell — the movie seems to be sliding, with a wink, into sinister realms of ancient folklore.

Back in London, “Amulet� starts to take on the familiar contours of a slow-to-boil romance, when Sister Claire swoops in and leads Tomaz to the home of a woman, Magda (Carla Juri), who looks both wary and weary. Magda’s home is a marvelous ruin; the walls are cracked and moldy, there’s no electricity and the less said about the plumbing, the better. (The expertly grotty production design is by Francesca Massariol, the atmospheric cinematography by Laura Bellingham.) Howls of agony issue forth from some upstairs bedroom; that’s Magda’s mother on her deathbed, Sister Claire explains, right before telling Tomaz that he’s welcome to stay, so long as he helps out with odd jobs around the house.

Some jobs are odder than others, and after making a few gruesome discoveries — one of them in perhaps the freakiest backed-up-toilet scene since “The Conversation� — Tomaz concludes that Something Very Wrong is afoot and that Magda is in desperate need of rescue. Notably, this isn’t the first time Tomaz has cast himself as a potential savior. Cue those wartime flashbacks, in which we see Tomaz offering aid to Miriam (Angeliki Papoulia), an anxious runaway who’s desperate to slip across the border. Tomaz gives Miriam food, shelter and company, plus a few lingering glances that suggest his motives for helping her might not be entirely altruistic.

Who is Tomaz, what does he want and what has he done? It’s clear from the beginning that he has his demons, which doesn’t make him any less sympathetic at first. Secareanu, a Romanian actor who costarred in the splendid romantic drama “God’s Own Country,� is a naturally involving screen presence, something “Amulet� uses to its sly advantage. Garai finds ways to undermine everything we think we know and trust, starting with a few extreme closeups that directly reference Hitchcock’s “Psycho,� another movie about a guilty visitor, an oppressed host and a domineering mother.

“Psycho� isn’t the only horror classic to which “Amulet� tips its hat. Garai, whose work as an actor includes English period dramas like “Atonement,� “Suffragette� and the BBC series adaptation of “Emma,� is an enthusiastic devotee of the bump-in-the-night canon. This is a haunted-house movie whose phantoms seem both supernatural and psychological, and whose horror inspirations run the art-house gamut from Jennifer Kent’s “The Babadook� to David Cronenberg’s “Spider.� The influence of Italian master Dario Argento, best known for “Suspiria,� can also be felt in the picture’s increasingly outlandish flesh-and-blood imagery and, most pointedly, its shifting focus toward the women in the story.

To say more about what “Amulet� is really about would rob the movie of its element of surprise; it would also deflate the power of a second act that seems alternately too concrete and a little vague in its subversions of the genre template. That said, a second viewing of the movie pays its own fascinating dividends: Watch it again and you’ll notice how much of the drama plays out not in the frenzied shrieks and memorably grotesque effects, but rather in the wordless, watchful expressions of the female characters inhabiting the margins of Tomaz’s psychodrama. Garai gives voice to their silent fury and unmistakably adds her own, building a howl of rage that before long has come to sound like a chorus.