Hugh Grant Is Genteelly Terrifying

You’ve heard of “faith-based movies”? Well, “Heretic” is essentially the opposite. In A24’s thorny, impossible-to-anticipate thriller, co-directors Scott Beck and Bryan Woods (best known as the writers of “A Quiet Place”) ask audiences to accept Hugh Grant as a demented religious scholar so extreme, he’s arranged to trap two Mormon missionaries in his house and torment them into rejecting their faith in Joseph Smith and all his teachings.

The lesson this sicko has planned is to Bible study what “Saw” is to shop class. But this is Hugh Grant we’re talking about. When his character, the innocuously sweater-clad and bespectacled Mr. Reed, answers the door, the young pair have no reason to question his motives, or his generous offer of fresh-baked blueberry pie.

These two proselytizers have come selling salvation. Beck and Woods are selling something else — namely, suspense — counting on Grant’s radically against-type turn to keep audiences on their toes. Which it does. The likable English actor has been branching out of late, playing shady characters in Guy Ritchie movies and even a comic villain in “Paddington 2,” but he’s never gone anywhere near as dark as “Heretic” demands. That’s both the movie’s selling point and a flaw in its own logic.

Talky and thought-provoking, yet shallower than it sounds at first, Beck and Woods’ screenplay has more on its mind than most horror movies. But why is “Heretic” a horror movie at all? Beck and Woods’ ideas surely would have been more effective as a university-set tête-à-tête — a fiery back-and-forth between two self-righteous young pupils and their smugly skeptical professor, perhaps — but start to feel not just nihilistic but borderline irresponsible once Mr. Reed’s intentions become clear.

“Heretic” opens with Sister Paxton (Chloe East) and Sister Barnes (Sophie Thatcher) sitting on a park bench, discussing Magnum condoms. Paxton heard they’re the same size as regular condoms. It’s a strange conversation for two abstinent members of the Church of Latter Day Saints, and feels suspiciously like the kind of gimmick meant to grab readers’ attention on Page 1 of a spec script (whereas audiences have already bought a ticket and don’t need the same convincing to carry on).

Neither Paxton nor Barnes has the personal experience to say whether their Magnum theory is true, but they’re skeptical enough to question the sales pitch. That’s what Mr. Reed (as Grant’s character is named) wants them to do as well. He gave his contact info to the Mormon missionaries. He invited them into his home. And now that they’re here — a captive audience to his mostly one-sided theological debate — he wants his guests to acknowledge that they are just glorified salespeople, spreading the word on a bogus religion.

For most of “Heretic,” Mr. Reed isn’t really speaking to Paxton and Barnes. What interest could he possibly have in converting them to his way of thought? Rather, he’s addressing the audience, who are likely more willing to agree with him than a pair of door-to-door evangelists indoctrinated into their parents’ faith. (In Barnes’ case, it’s slightly more complicated, as she had a near-death experience when younger that sets up one of the film’s less-developed dead-ends.) Meanwhile, Beck and Woods keep us squirming by drawing out scenes and delaying whatever fate awaits these two missionaries.

Once Mr. Reed lures the girls to his inner sanctum, he presents them with a test. The room has two “exit” doors, on which he scrawls the words “BELIEF” and “DISBELIEF” in chalk. Choose correctly, and they’re free to leave … or so he says. But can they trust him? His home has been expressly engineered for this purpose, with doors and windows that lock and metal-plated ceilings and walls that block cell-phone signals.

Mr. Reed seems to have thought of everything. In this space at least, he’s free to play God — or pedagogue, as he seems to prefer, preaching what he calls the “one true religion.” Mr. Reed uses pop-culture references to make his case, suggesting that all religions are “iterations” of one another, the way The Hollies’ “The Air That I Breathe” inspired Radiohead’s “Creep,” which in turn likely influenced Lana Del Rey’s “Get Free.” But what does that prove, since the differences between religions are often more revealing than their similarities?

“Religion is regarded by the common people as true, by the wise as false and by rulers as useful,” spoke Seneca, summing up most of the discussion (and dissection) Mr. Reed has in store. He’s the smartest person in the room, and yet, something doesn’t quite add up in the way he tries to demonstrate how such systems are used to manipulate and control the masses, forcing the filmmakers to resort to scuzzy horror-movie gimmicks — and a convoluted stunt Mr. Reed calls his “miracle” — to keep us hooked.

Fortunately, the two missionaries are not as callow as they look. Sister Paxton is polite and eager to please, but eventually sees through Mr. Reed’s argument and asserts herself as needed. Like a young Winona Ryder, Sister Barnes has a tough edge and secrets of her own. But the most unpredictable character is Grant’s, since nothing he’s done before quite prepares us for what he’s capable of here. It’s scary, to be sure, but it doesn’t necessarily add up. These two aren’t Mr. Reed’s first victims, but where does he find them? (A barely recognizable Topher Grace makes a brief appearance as Elder Kennedy, who’d surely catch on if missionaries assigned to Reed’s house kept disappearing.)

Come to find, fear and religion aren’t so different. They both rely on what we believe … and it takes a leap to accept the stammering fellow from “Four Weddings and a Funeral” as someone this twisted. Go with it, and “Heretic” can be an entertaining ride. It may not change your mind about religion, but you’ll never think of blueberry pie the same way again.