Six years after the U.S. Army dumps gallons of aging formaldehyde into Seoul's Han River, a mutant sea monster emerges from its depths and begins to terrorize the populace. Most affected are the family of food-stall owner Park Heui-bong (Byeon Heui-bong), whose granddaughter, the teenage Hyeon-seo (Ko A-sung), is captured by the slime thing and spirited off to a secret lair.

Claiming the monstrosity is carrying some sort of horrifying virus, the Korean government decides to quarantine all those who've come into contact with it. In the meantime, the U.S. government alleges they have a new weapon, Agent Yellow, that will rid Korea of the plague, and plans to spray the chemical compound over the city.

Escaping from the quarantine, the Park family sets off in search of their lost member. The squabbling members, all brilliantly portrayed, include Bong's daughter Nam-ju (Bae Du-na), a top-ranked archer; Bong's son, Gang-du (Song Gang-ho), a total slacker and doofus; and Gang-du's younger brother, Nam-il (Park Hae-il), a jobless graduate and former student radical. Their desperation, and the worst-laid plans of the Korean and American authorities, combine to create an apocalyptic finale that is as horrific as it is emotionally satisfying.

Director Bong Joon-ho, whose last film was the memorably offbeat serial-killer flick Memories of Murder, has managed to subvert even more genres in The Host. Thanks to top-notch special effects and slam-bang direction, the film totally works as a prime gore-fest. But because it never takes itself too seriously, and is filled with quirky characters and moments, the picture is also gut-splittingly funny. And then there's the political element: The Park family are stand-ins for all the "little" people who have been crushed by insensitive and cruel government bureaucracies. Their struggle to find the missing Hyeon-seo, despite all the roadblocks put in their way by various governments, is often absurd, but also incredibly heroic.

Yet even when he's making these heavy political points, Bong never pounds his message home. It's all in the context of a wonderfully weird, and hugely entertaining, genre exercise that should please all sorts of audiences, whether art-house types or fanboys. The Host is one hell of a ride.