Hugh Grant bedevils in Heretic, a theological debate wrapped in horror trappings

What is the one true religion?

This theological question is at the heart of Heretic, a Gothic horror show that probes the mysteries of faith and the capacity of evil.

When Sister Barnes (Sophie Thatcher) and Sister Paxton (Chloe East) turn up at Mr. Reed's (Hugh Grant) door, hoping to convert him to the Church of Latter-day Saints, what they find is an absent-minded, middle-aged man, charmingly befuddled in the way only Grant can be. But things quickly take a turn as Reed engages the girls in theological debates while the lights go out, and the front door locks and refuses to budge. Soon, the girls find their faith put to the test in a trap designed to test their beliefs and measure their conviction.

Scott Beck and Bryan Woods, who co-wrote and helmed the film, direct with atmospheric fervor, employing pouring rain, leaky roofs, and dimly lit spaces to eerie effect. Reed's house — both as seen from the gate in beautifully crafted shots through the wrought iron and as revealed on the inside — emanates an unsettling energy that is reminiscent of a Gothic house of horrors. In contrast, Grant gives a performance that moves from disarming curiosity to cheerful cruelty, all while clad in a patchwork sweater and sensible sneakers.

Grant exudes an almost obsequious congeniality before letting something more sinister seep from his pores. The last several years of his career have been marked by bold and interesting choices — and this might be his most wildly wicked role yet. Taking some of the smug villainy he so deliciously showcased in Paddington 2, he replaces ego with menace, creating a sense of dread from his disturbing calm and false brightness as he spins a web for these two young women. Grant molds Reed a practiced mask of feigned confusion, but we know something far worse is afoot as we watch Reed's sick pleasure mount alongside the girls' rising terror.

Grant also recognizes that humor is essential to a film like this, whether it be to cut tension or to lend a deeper layer to Mr. Reed. He's always been a gifted comic actor, and Heretic is a thrillingly different vehicle for those talents propelled by his eerily infectious glee. He presents religious arguments with his signature dry wit and pulls strings with a droll puppet-master energy.

The two actresses who face off against him are admirable adversaries. Thatcher sells Barnes's doubt from the start, highlighting her worldliness and her far more intellectually considered interpretation of her beliefs. East is her foil, a naive innocent raised within the strictures of Mormonism, which she's never stopped to question. As the horrors of their situation accelerate, she gives an arresting performance, still never surrendering Paxton's twinkle of blind faith, even as she is forced to remove her rose-colored glasses.

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Beck and Woods build fear and tension through close-ups, pregnant pauses, and a meticulous edit that masters the film's pace. The first half of the film is more unsettling than horrifying. The script and Grant employ humor and apt analogies in ways that truly invite the audience to engage in the spiritual questions being presented while remaining on alert. Reed does make many valid points about ecumenical hypocrisy and the iterative nature of organized religion. Until he doesn't.

Heretic keeps you guessing, obscuring its plot twists and holding back Reed's sinuous motives and master plan. To say more would spoil the film, but suffice it to say that never has pondering theology been so devilishly entertaining — and amen to that. Grade: B+