In the past 15 years, South Korea has experienced the most staggering cinematic renaissance since Easy Rider and Midnight Cowboy ushered in independent American filmmaking. The current wave riffs on the country's rapid technological growth, the disconnect between generations, police incompetence and the North-South divide. With visually hyperkinetic storytelling heaped with unexpected dollops of humor, Korean directors have embraced genre filmmaking while forging new ground.

Yet even the country's most revered filmmakers have had trouble transitioning to English-language cinema. Park Chan-wook—of Oldboy, Thirst and Lady Vengeance—flopped with Stoker, an elegant but ultimately cold thriller. With The Good, the Bad, the Weird, Kim Jee-woon made one of the craziest action films in recent history, only to turn the Schwarzenegger comeback vehicle The Last Stand into a merely serviceable action yarn.

Expectations for Bong Joon-ho's Snowpiercer were astronomical. This is, after all, the most expensive Korean movie yet made, helmed by the director of The Host, a tender meditation on family disguised as a monster flick that was the country's most successful film ever. His follow-up, Mother, was a heart-wrenching master class in suspense and mystery. The two films established Bong as a genre-hopping wunderkind of immense vision.

With memories of the disappointing Elysium still fresh, Snowpiercer sounds suspect. The film, loosely based on a 1982 graphic novel, is built around a similar class-warfare metaphor: It's a dystopian parable set during a human-induced ice age in which the remnants of the human race populate a self-sustaining train endlessly circling the globe. The rich live in the front of the train, where they're treated to steaks and pedicures. The poor are relegated to the back, where they're beaten by guards and subsist on mysterious protein bars.

That sounds like a simple enough premise for a ham-fisted sci-fi tale. Yet Snowpiercer is so much more. It is grim, violent, hilarious, strange and smart. It's the most inventive science-fiction picture in years, the most original action film in a decade and perhaps the most all-around entertaining movie so far this year.

The story centers on a revolution led by Curtis (Chris Evans, breaking free of Captain America's tights) and sidekick Edgar (Jamie Bell), who take a mob from the train's caboose to its engine. The front of the train holds many promises, among them windows and hard-boiled eggs. It also offers a reckoning with Wilford (Ed Harris), the train's designer and the man whose vision of a perfect society includes segregation, as well as vengeance against Mason (Tilda Swinton, stealing the movie), a toothily Thatcherian overseer who uses creative torture to control the masses. She provides the film's most chilling and hilarious moments, including a propaganda-filled tirade precisely timed to match the seven minutes it takes a dissenter's arm to freeze solid when forced outside the speeding train. It's at once terrifying and ridiculous, hammered home by Swinton's over-the-top menace. 

Snowpiercer follows its dirt-smeared heroes as they move from car to car, assisted by a security expert (The Host's great Song Kang-ho) with a secret agenda. Each car is a new environment: Sometimes it houses a horde of masked, ax-wielding thugs ready to quash the revolution. Sometimes it contains a classroom full of propaganda-addled children. Sometimes there's a sushi bar. Never is it expected.

Some might fault the way scenes jackknife from hallucinogenic serenity to a close-quarters gunfight, all the while piling on enough surrealist, dystopian imagery to fuel the rest of Terry Gilliam's career (hell, they even name-check the 12 Monkeys director). Some might consider its political allegories too on-the-nose. But a little heavy-handedness can be forgiven when the result is this bracing.

Snowpiercer plows forward with gleeful abandon, confirming that Bong—with a style of storytelling that is visceral and an imagination that is endless—is one of the best directors of his generation.  

Critic's Grade: A

SEE IT: Snowpiercer is rated R. It opens Wednesday at Cinema 21 and the Hollywood Theatre.