Seoul 2006. Hee-bong runs a snack bar on the banks of the River Han where he lives with his family. Gang-du, his elder son, is an immature and somewhat slow-witted fellow of 40. Nam-joo, his daughter, is a archery champion and member of the national team. Nam-il, his last son, is an unemployed shirker. They all are overprotective of little Hyun-seo, the daughter of Gang-du, whose wife left home long ago. One day, an unidentified monster suddenly appears from the depths of the River Han and spreads panic and death. Little Hyun-seo is carried off by the monster and disappears before her father's very eyes. Hee-bong's family has lost what was dearest to them. It decides to wage a crusade against the monster.