If you don’t recognize this person, there’s a distinct possibility it’s you. There’s no shortage of discussion surrounding religious zealotry, those from any faith seeking every opportunity to convert others to their cause, but the flip side is just as prevalent. Call them born again Atheists or crusaders against theology, these godless folk would like nothing more than to talk your ear off about the infeasibility of an all-knowing power, the concrete data that renders all disagreement futile, and the foolishness of those who organize their lives around faith and belief. Their stance and attendant mode of delivery isn’t so far removed from the sign-carrying, megaphone-wielding street preachers on the other side of the divide, an unwitting kinship that writing/directing duo Scott Beck and Bryan Woods seems keen to weaponize. After all, turnaround is fair play. Forced captivity… now that’s a different story.

Heretic’s tale of entrapment, observed literally but also through twin veins of piety and devotion to a cause, begins long before our characters are aware of the snare. Rounding out a day spent pounding the pavement, mormon missionaries Sister Paxton (Chloe East) and Sister Barnes (Sophie Thatcher) make one last call to the home of Mr. Reed (Hugh Grant), an outwardly affable Brit who’d like to exchange a quick word on his theistic findings. Their cordial back-and-forth, set to a backdrop of pounding rain, devolves from niceties into antagonism before taking another, more sinister turn when the young women realize that all the exit points of Reed’s home have been locked from the outside. A night of terror awaits, but not before an avalanche of condescending monologues.

He will go on. Possessed with considerable intellect and not even a modicum of modesty, Reed is high-minded and verbose to the point of parody, splitting the difference between dubious mansplainer and over-eager podcast host. Beck and Woods’ screenplay is full of enviable morsels, but a finely-tuned dexterity in the art of one-sided conversations is its greatest accomplishment, a form of discourse wherein attendees are all output, no input. Heretic is surprisingly funny, filled to the brim with enough galaxy-brain metaphors and 1,000 thread count tension to prompt more tentative audience members to giggle, but its greatest joke is also its least laughable. Being caged in the home of an unhinged madman might be nightmare fuel, but it’s nothing compared to hearing out his breathlessly articulated, egomaniacal ravings on society’s shortcomings.

At least giving them a winsome voice softens the blow, and Grant is perfectly attuned to the role of merry menace. It’s hard to think of an actor more at home as an eloquent charmer with devious undergirding, or one who would sink their teeth in with this level of evident joy and playfulness. It goes without saying that the Love Actually and Music & Lyrics alum isn’t used to having such sinewy dialogue at his disposal, and his nimble delivery of Beck and Woods’ writing is something to behold. East and Thatcher aren’t blessed with the meaty stuff, but the former, who nearly stole the last hour of The Fablemans in a similarly effervescent turn, is making a name for herself as a bubbly performer with something else going on behind her eyes. Thatcher is also carving out a mold, moving her steely gaze from one gloomy project to the next with a speed that could make fellow ascendant genre starlets like Jenna Ortega or Yellowjackets castmate Ella Purnell green with envy. No one here is breaking form, but the pieces fit like a glove.

The same description of snugness applies to the film’s claustrophobia-inducing setting, though our pair of helmers have answers here too. Set almost entirely in the aforementioned house, production designer Philip Messina’s work is too small in scale to warrant hosannas come Oscar time, but his leering residence never makes you want for space. Fitted with innumerable trap doors and hidden compartments, the set also benefits from set decorator Hamish Purdy’s cagey inclination toward sparsity, with just enough on the walls and tables to seem livable, but not lived in. It all comes to life through cinematographer Chung-hoon Chung’s wicked lens; the Oldboy and Last Night in Soho veteran is no stranger to creating tension in tight spaces, and his love of close-ups gives the movie its tense, sweaty edge.

There is, however, no level of craftsmanship that can bring the set pieces here up to the quality of everything else, but perhaps Beck and Woods’ relative lack of interest in the film’s more grisly attributes simply mirrors our own. Despite being billed as a horror/thriller (and laying claim to enough tension to merit the designation), Heretic works better as both an ideological battleground and a cheeky dark comedy than it does as a frightener, with the devilish games on hand, and their requisite flights of terror and gore, mostly playing like tacked-on homage to the Saw franchise. Those movies are also set in a field ethical rhetoric, but prioritize their feats of ghastly imagination over the philosophy seminar. Heretic inverts the recipe, causing its last 30 minutes, wherein blood is let and secrets are revealed, to feel like cinematic autopilot.

Concluding with your weakest material isn’t the best look, and it’s hard to fault anyone who gives Heretic a less than sterling review after the plane’s rocky landing. That final act is likely to deny the film of the reputation that it otherwise deserves, but a near-perfect introductory hour shouldn’t go unnoticed. The balancing act here, which pits studied, laborious doubt against dogmatic, durable fealty, is marvelously even-handed, an objective stance that will be read as leaning this way or that depending on the scene. The refusal to land on either side of the aisle, and steadfast insistence that the two paradigms are mirror images of one another, is refreshing and exciting, making appointment viewing out of whatever Beck and Woods decide to do next. It might not have a worthy culmination, but for the majority of the runtime, we’re just like sisters Paxton and Barnes: a captive audience.