In the mood for allegory? Have a look at Bong Joon-ho's "Snowpiercer," which proceeds from a fantastical premise rich with real-world relevance. After a human-engineered planetary catastrophe (trying to arrest the planet's warming, we accidentally froze it solid), the remaining people are stuck on a train that never stops moving. A few thousand survivors live in railway cars, sorted into a rigid and ruthlessly enforced social order.

In the back are huddled masses fed on gelatinous, insect-based black protein bars and kept in line by a combination of propaganda and brute force. Toward the front, the more fortunate enjoy access to schools, nightclubs, fresh food and the reassurance that they deserve everything they have. An unseen, quasi-mythical entrepreneur is in charge, and a group of rebels has decided to challenge his power and the extreme inequality he represents.

But perhaps you'd prefer an action movie. "Snowpiercer," based on the graphic novel "Le Transperceneige" by Jacques Lob, Benjamin Legrand and Jean-Marc Rochette, is unusually satisfying in that regard as well.

Bong, whose previous films include the brilliant psychological thriller "Mother" and "The Host," a sublimely moving monster flick, is a playful and rigorous visual thinker. Here he stages kinetic fight scenes in narrow spaces and punctuates the noise and speed of the train with moments of eerie, poignant calm as it glides through digitally rendered ice and snow. The violence inside swerves from slapstick to bloodshed and back, producing a volatile blend of humor and horror that pays tribute to the source material while coloring its themes with the director's distinctively perverse and humane sensibility.

And if acting is your thing "Snowpiercer" will not disappoint. The reluctant leader of the rebels, a back-of-the-train troublemaker named Curtis, is played by Chris Evans, his clean-cut Captain America charisma obscured by scruffy facial hair and a black wool watch cap. He is a stoical, heroic presence amid the chaos, which means he has less room to be interesting than the other actors, who provide some of that chaos. They include Octavia Spencer, John Hurt and Jamie Bell as some of Curtis' fellow insurgents, whose careful planning and simmering resentments blossom into revolt after an especially cruel provocation by the authorities.

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There are soldiers in riot gear, armed with clubs and guns, but for Bong evil is never anonymous. He gives it a grotesque, human face -- or rather a series of faces, most memorably Tilda Swinton's, almost unrecognizable in prosthetic teeth and oversize glasses. She serves as a kind of spokeswoman for Mr. Wilford (Ed Harris), the enigmatic engineer who is both dictator and deity in this postapocalyptic world.

As the train moves in its long, winding route around the globe, teetering on the edge of both sustainability and plausibility, Curtis and his comrades undertake a long march toward the engine. They are joined by Minsu (the great shape-shifting South Korean actor Song Kang-ho), a security specialist, and his daughter, Yona (Ko Ah-sung), both addicted to an inhalant called Kronole.

Bong is interested above all in imagining how the whole thing might work, as a matter of technology and social organization. And so every episode of fighting or conspiring is accompanied by a dollop of exposition, some of it recalling the start of the journey (18 years before the action takes place), some surveying its present condition and some looking around for clues about whether or how it might end.

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At times, "Snowpiercer" recalls Terry Gilliam's "Brazil," both in its steampunk décor and in its grimly satirical look at the workings of power and privilege in a totalitarian corporate future. Its lessons about human nature are thought-provoking, but perhaps not as memorable as its motley, eccentric display of humanity in extremis. And though the movie is playfully postmodern in its pastiche of styles and its mingling of sincerity and self-consciousness, there is also something solidly old-fashioned about the way it tells its story. Long, crowded and ambitious almost to the point of hubris, it reminded me a little of "The Poseidon Adventure" and other 1970s-vintage action allegories full of great actors struggling to survive.

That's a compliment, by the way. Disaster has become a matter of routine at the movies (in more ways than one). Planetary destruction and human extinction happen a half-dozen times every summer. It's rarely this refreshing, though.

"Snowpiercer" is rated R. The language is rougher and the violence grislier than in most summer action movies.