Of all the recent movies about a dystopian future, “Snowpiercer” has one of the silliest premises—which is saying a lot. But thanks to the skill of Korean director Bong Joon-ho, it proves one of the best of the genre. It may not be the brightest movie around, but it’s almost insanely watchable.

The conceit, derived from a 1982 graphic novel by Jacques Lob, Benjamin Legrand and Jean-Marc Rochette, is that an effort to combat climate change by unleashing a chemical into the atmosphere resulted, some eighteen years earlier, in a new ice age that killed off most of the population and rendered the earth uninhabitable. A small group has survived aboard the titular train, built by an oddball mogul named Wilford (Ed Harris), which speeds endlessly around the globe via a perpetual-motion engine and a grill that easily barrels through any ice buildups that form on the tracks.

The society on the train is strictly divided into classes. In the rear are the poor, hapless masses dependent for sustenance on the oily black bars of suspicious content provided by the ruling elite upfront, who live high lives. The ragtag mob live in crowded, filthy conditions, and are treated brutally, with their children periodically rounded up and taken away. And anyone who shows signs of resistance is punished by gun-toting storm troopers directed by Wilford’s adoring factotum Mason (played by Tilda Swinton with bulging eyes, a north English accent and fearsomely large front dentures). There have been attempted uprisings in the past, we’re told, but all have failed to reach the front of the train.

Now another rebellion is being planned, encouraged by brief messages from someone upfront that are secreted in capsules in the food bars, with the leadership falling on the reluctant Curtis (Chris Evans, looking very un-Steve Harris-like with black hair and beard). He’s advised by frail elder statesman Gilliam (John Hurt) and aided by a trio of agitators: eager young Edgar (Jamie Bell), whose loyalty to him is unbounded, Andrew (Ewen Bremner), who lost an arm to the troops, and Tanya (Octavia Spencer), an angry woman whose adorable child was recently abducted by the Wilford crowd. The uprising enjoys some initial success when Curtis realizes that the storm troopers’ guns are empty, and he seizes the opportunity to break into a forward car to free from suspended animation—per instructions from the mysterious mole upfront—a Korean engineer, Namgoong Minsu (Song Kang-ho), who’s familiar with the Snowpiercer’s security setup and able to unlock hatches leading to the engine. Namgoong demands compensation for his assistance, however: the liberation of his daughter Yona (Ko Ah-sung), along with a dosage of a hallucinogenic drug called kronole for every hatch he opens for the rebels.

The rest of the film follows Curtis and his band as they make their way through car after car—the schoolroom car (with a gleefully propagandistic teacher played by Alison Pill), the garden car, the meat car, the aquarium car, the dining car, the luxury spa—until they finally reach the entrance to the engine where the semi-divine Wilford holds court. Along the way they must deal with not only Mason and her troopers, but Wilford’s formidable enforcer Franco (Vlad Ivanov) in a series of violent action scenes that show plenty of choreographic imagination, and not a few surprises, death-wise. In the end, however, the progress of the rebellion proves a far more complicated business than it seems at the surface, with revelations in the last reel during a conversation between Curtis and Wilford that point up the manipulative power of the ruling class.

Clearly “Snowpiercer” has a strong, none too subtle socio-political message to advance, and in truth it’s hardly subtle about doing so, or about making character points through elaborate monologues dropped into the proceedings to provide back stories for major figures. But even if you find its economic stance, which contrasts the squalor of the train’s rear with the utter decadence at the front, a ludicrously oversimplified microcosm of the capitalist system, Bong presents it with such style that it’s impossible not to be drawn into the world he creates with his cinematographer (Hong Kyung-Pyo), production designer (Ondrej Nekvasil), art director (Stefan Kovacik), set designers (Adela Hakova, Petr Bouska, Darina Hejlova, Pavel Tatar and Barbara Garcia), set decorator (Beata Brendtnerova) and costume designer (Catherine George). Nor should the glimpses of the frozen outdoors supplied by the effects team be overlooked, even though the shots of the train speeding along have a model-based feel. The moodiness of the piece is accentuated by the poised editing of Steve M. Choe and Changju Kim, and by Marco Beltrami’s powerful score, which represents some of his best work.

The cast responds with obvious commitment, Evans providing the earthy earnestness, Bell the boyish enthusiasm, Hurt the grizzled wisdom, Spencer the seething anger, Bremner the wild-eyed fury and Song the rumpled cynicism. Swinton, meanwhile, offers another of her go-for-broke turns that’s amazingly reckless and totally absorbing, while Harris turns up late to present a pitch-perfect picture of the cool, smug heartlessness of entitlement.

“Snowpiercer” could be called an apocalyptic action movie, but it’s very different from most Hollywood examples of that genre in its dark tone, its deliberate pace and its intellectual ambition. Those qualities may bewilder or upset mainstream audiences, but they make it deliciously different from run-of-the-mill doomsday pictures, just as Bong’s “The Host” stood out from ordinary giant-monster fare. The Korean director makes movies that resemble the early work of Guillermo del Toro—the intriguingly offbeat ones he made before his turn to the Hollywood dark side. Let’s hope that Bong proves more adept at resisting the lure of complacent conventionality.