"The Host" is like a South Korean version of a Japanese monster movie. The cultural differences make it something the Japanese creature features never were: a nearly great film.

Packed with politics, family conflict and satiric references to some of the more absurd aspects of Korean cinema, "The Host" never forgets to be a scary, icky, over-the-top fright fest, either.

Directed by emerging genre masher Bong Joon-ho, whose 2003 "Memories of Murder" turned the police procedural inside out, "Host" starts with a neat-freak American military scientist insisting on flushing experimental biohazard material into Seoul's Han River. Several years later, a giant, carnivorous amphibian, which looks like an unholy cross between the "Alien" queen and something Guillermo del Toro might have dreamed up, rampages along the waterside.

One of its first victims is a bright little schoolgirl, Park Hyun-seo (Ko A-sung), whose comically irresponsible father Park Kang-du (Song Kang-ho) runs a riverbank snack stand. Though presumed dead by all - the mass memorial for the monster's victims is an emotionally florid scream - Hyun-seo manages to get a brief cell phone message to her father. She's trapped in the creature's putrid lair, but Kang-du can convince only his equally wacky relatives (his sister Nam-joo, played by otherworldly beauty Bae Doo-na, is a competitive archer with a distressing tendency to hesitate on the draw) that Hyun-seo must be found and saved.

Anyway, as various Parks commence their highly eccentric searches for the girl, she does her best to escape the Host while protecting a younger child it's brought home. This is terrifically unnerving stuff, and is matched for tense excitement by the wildly excessive climax of the whole crazy monster hunt.

Meanwhile, anyone familiar with Korean history will appreciate how Bong weaves in themes of social protest, authoritarianism and division, while having a field day with the kind of sadistic extremism that seems to work its way into even the most benign of his nation's movies. Beside the monster's depredations, be prepared for medical torment and bureaucratic indifference refined to a fine instrument of torture.

The monster, which is frightening despite a bug-eyed comical look, is the offspring of several world-class effects houses, including Peter Jackson's Weta Workshop and the U.S.-based Orphanage, which contributed to the last Harry Potter movie. The results are impressive but look just cheesy enough to evoke fond memories of Godzilla devastating cardboard Tokyo.

Yet, even with its comic exaggeration, "The Host" leaves us thinking that if this kind of thing really happened, it just might unfold in something like this peculiar way. I can't recall any other monster movie that's worked out the details well enough to have that effect. *

In Korean with English subtitles. Produced by Choi Yong-bae, directed by Bong Joon-ho, written by Baek Chul-hyun, Bong Joon-ho and Ha Won-jun, music by Lee Byung-woo, distributed by Magnolia Pictures.