As The Host (or as listed in Korean in the new IMDB, Gwoemul) begins, an arrogant American military guy (Scott Wilson, best known recently as Catherine Willowes' ring-a-ding-ding daddy on CSI) orders his Korean underling to pour hundreds of bottles of formaldehyde down the drain. "But these drains empty into the Han River," protests the underling. Exactly.
When we flash forward, we're on the river shore in Seoul, where a fractured and amusingly fractious family (Grandpa, Hie-bong Byeon; slacker Dad, Kang-ho Song, with a peroxided fringe; and sweet granddaughter/daughter, Hyun-seo, played by Ah-sung Ko) run a snack stand. But barely have we figured out the family relationships when a huge nasty sea creature that looks like a ferocious polliwog and runs like a lizard on speed crawls out of the ocean, threatens tens of funseekers, and grabs Hyun-seo, diving back into the Han with her in his ugly mouth.
The Host follows what happens to threatened schoolgirl Hyun-seo, who survives being grabbed by the sea monster, while focusing mostly on her family, both grandpa and slacker dad, along with slacker dad's siblings -- his sister the national bronze medalist in archery and his brother the snotty and unemployed college graduate -- as they discover that their beloved Hyun-seo is alive and plot to save her. At top and bottom, The Host is a creature feature, with excellent production values and a scary creature that moves so quickly that we never get a real fix on its appearance, which makes it seem even scarier. This is not Godzilla, except in the beast's origins; this is a very well-made film.
In its middle, however, The Host offers not just suspense but hearfelt family comedy; while this is not Little Miss Sunshine transposed to Korea, this family is both challenged and contentious. A brawl at Hyun-seo's memorial, before her slacker dad discovers she is alive, is dark fun. The clearly focused satire on Korean government officials, who are either bumblers or nefarious plotters, is entertaining and pointed, as is the presentation of the Americans as the people who create the problem, then rush in and take over to supposedly solve the problem. (You think?)
Who is scarier, a mutant river creature or the American military? That's the question that The Host asks, and, given this film's basis in history (a U.S. military official did indeed order the disposal of formaldehyde in the sewer system leading to the Han), it's not difficult to conclude that the latter is a greater threat.