At the start of the giddily entertaining monster movie “Hope,” the director and screenwriter Na Hong-jin serves up a load of bull. No, really. We’re on the South Korean side of the Demilitarized Zone, and a large male bovine has been found slashed to death near an open field. Flies buzz over the rotting carcass, which is riven by claw marks so unnaturally deep that no one can determine whomauledit. A bear? Unlikely. Maybe, one man suggests, it was that tiger from the north—the one that, flouting the rules of peninsular diplomacy, often steals across the border in search of food. This is a joke, but a telling one; the characters in this movie are used to living on high alert. The small town that they inhabit may be called Hope Harbor, but it exists in an everyday purgatory of barbed-wire fences, undetonated land mines, and signs urging residents to “report spies” and “protect the nation against infiltration.” Who could have guessed that their worst enemy would hail not from across the border but from the skies?

The people of Hope Harbor don’t know it yet, but an alien invasion is under way—and Na, a horror-thriller maximalist of uncommon patience, takes his time breaking the news. Subscribing to Spielberg’s law, definitively proved in “Jaws” (1975), that the predators we don’t see are the ones that scare us the most, the director spends the first of this movie’s two and a half hours methodically setting the scene—which, in this case, means laying waste to the scenery. Rattled by the mystery of the bull, Bum-seok (Hwang Jung-min), the bumbling, trigger-happy police chief of Hope Harbor, drives back into town and is confronted with a disaster zone. “A freaking huge monster,” in the words of an irascible eyewitness, has torn through the village, gutting shops and homes and leaving bodies strewn amid the rubble. The cinematographer, Hong Kyung-pyo (“Burning,” “Parasite”), slows the camera to an ominous crawl as Bum-seok draws his weapon and tiptoes through the debris: broken beams, caved-in ceilings, bloodstained tiles, and piles upon piles of precious, ordinary, soon to be forgotten stuff. Admirers of Na’s previous films, none more bewitchingly bonkers than “The Wailing” (2016), will recognize the cluttered crime-scene handiwork of his longtime production designer, Lee Hwok-young. Buildings, like bodies, have innards, too.

There’s a dread-soaked wit to the movie’s drawn-out approach, especially in this first hour. We may think that we’re seeing the aftermath of a creature’s rampage, but we are, in fact, being introduced to the creature itself: we are what we destroy, Na seems to be saying. From this particular trail of devastation, we can deduce that the perpetrator is colossal, fast, and possessed of a strange mix of clumsiness and stealth. As Bum-seok zeroes in on his target, Na lures us into a crafty game of predator peekaboo; we can track the monster’s proximity through the explosions that it triggers in the vicinity and the lethal projectiles that it lobs from afar. Na is so good at this brand of menace by misdirection that, by the time you finally lay eyes on the monster, you might wish you hadn’t. For one thing, the creature, whom the end credits call Va’migere (and who is played, via performance-capture technology, by Cameron Britton), is properly fearsome to behold: an unjolly green giant that chases after Bum-seok on all fours, shrieks like an emphysemic banshee, and generally brings to mind the love child of the Incredible Hulk and “The Exorcist” ’s Regan MacNeil. But it is also, deflatingly, a computer-generated creepy-crawly, and unlike some other movie monsters—say, the amphibious kidnapper from “The Host” (2006) or the sharp-eared stalkers from “A Quiet Place” (2018)—Va’migere has a humanoid face and form, rendered with an almost hyperreal incongruity. It might have wandered, or crashed, into the movie from a decade-old zombie-apocalypse video game.

Na’s solution to this problem is speed: the faster he can keep his aliens moving—Va’migere, alas, is not alone—the less likely we are to scrutinize the malevolent jumble of pixels they are. The film’s first chase is a tour de force of kinetic delirium: Sung-ae (Hoyeon), a brave junior cop, drives Bum-seok through the streets of Hope Harbor, with Va’migere sprinting furiously after them. Hong, favoring a backward-facing view of the mayhem, shoots in lengthy takes that swerve and snake with rough-and-tumble precision; the energies of car and camera seem to fuse into one. Compare this with a similarly arresting later sequence, set deep within a magnificently mossy forest, where a band of hunters, led by Sung-ki (Zo In-sung, full of rascally charisma), do battle with Va’migere’s alien friends. If the street chase transplanted “Bullitt” to the D.M.Z., this earthier showdown, which puts Sung-ki and his fellow-fighters on horseback, has the verdant majesty of a woodland Western.

Here and elsewhere, Na stretches out the action to an almost luxuriant degree, and he makes a virtue of attenuation: a run-and-gun stunt that seems repetitive the third time is somehow smashing on the eighth. It helps that the aliens are almost as hard to kill as Wile E. Coyote, and, indeed, should you emerge from “Coyote vs. Acme” with your craving for comic violence unsated, you might consider going straight into “Hope,” which is something of a live-action cartoon writ large. (There’s a touch of the Tasmanian Devil to the way Va’migere crashes through walls, leaving behind vaguely Va’migere-shaped holes.) Yet Na also insists on treating his aliens as objects of contemplation and pathos—reflections of our own misshapen humanity. In one slow-motion scene, we peer into Va’migere’s wraithlike visage and see not just rage or monstrosity but an all too relatable terror. We are what we destroy.

All four of Na’s features were shown at the Cannes Film Festival, but “Hope” was his first to appear in the main competition. Predictably, its selection triggered the kind of reflexive critical grumbling that often ensues when a gory genre movie, be it “Oldboy,” “Drive,” or “The Substance,” is elevated to the highest of world-cinema pedestals. For some of us, though, Na’s upgrade seemed overdue. His films, all of which have been critically and commercially successful, have long blurred the lines between the aspirations of the art house and the pleasures of the grind house. I still can’t shake the grisly final moments of “The Chaser” (2009), a blisteringly cynical police procedural that takes a hammer to the mere notion of competence or integrity in law enforcement. Na’s films are propelled by brutal individual acts, but they also swarm with systemic rot. His finest movie, “The Yellow Sea” (2011), strands a debt-ridden Korean Chinese immigrant in the midst of a mob war, forcing him to run and run—and kill and kill—in order to survive. It’s bleak as hell; it’s also exhilarating.

“Hope,” which is Na’s first film in a decade, represents both a step up in ambition and a step down in finesse. The movie has a goofy, galumphing beauty; it’s a bigger, dumber, shinier object than its predecessors, yet it also manifests the crudely violent small-town comedy that is one of Na’s signatures. The people of Hope Harbor speak almost exclusively in barked expletives and insults, and nearly all of them are packing serious heat; Bum-seok’s irritation at the sheer glut of unregistered weapons becomes a sly running gag. One colorful customer spouts a fabulously ripe monologue about how the aliens nearly caught him mid-defecation—a close encounter of the turd kind. More disquietingly, several of Na’s characters seem at least as fond of the art of disembowelment as their alien overlords are: witness an overeager coroner merrily firing up a chainsaw as she tackles her first alien autopsy, or a village doofus (Eum Moon-suk) whose unfortunate taste for taxidermy may have set this entire tragedy in motion.

Whom, exactly, are we supposed to root for here? Bum-seok, Sung-ae, and Sung-ki do find a shambolic Hawksian unity, after a fashion; Sung-ae, in particular, has only to step out of a car with a military-grade rifle to elicit spontaneous applause. But Na’s most interesting countermove is to seed the enemy ranks with Hollywood actors, including Michael Fassbender, Alicia Vikander, and Taylor Russell—not that you’re likely to recognize them under their gobs of shape-shifting C.G.I. Belatedly, Fassbender and Vikander, sweetly cast as a sort of alien couple, are given the most soulful lines in the entire picture, though whether soul is called for is unclear; a script that boasts a five-minute soliloquy about diarrhea is suddenly rife with mythical earnestness and impenetrable last-minute world-building. Is Na, in merging unforgettable spectacle and unutterable dialogue, laying claim to the mantle of “Avatar”-era James Cameron? Does he yearn to put the “Na” in Na’vi? Perhaps this saga of planetary conquest is also a sly commentary on Hollywood imperialism, in which even the most far-flung of small-town tales must be overwhelmed by big-name stars in visual-effects drag. Na has clearly succumbed to the blockbuster mentality: as he confirmed at Cannes, a sequel is already written. Could the next movie begin to make sense of its predecessor’s hilarious and confounding final minutes? Hope springs eternal. ♦