Opens in Bangkok in mid-April during Song Kran, a festival where the entire country gets into public waterfights. Then cuts to Hong Kong, where Fan Ko's dying father wants his son to quit his civil engineering job to take over his boxing school. Then father tells him a secret - he had another son with a Thai girl. To honour his father's dying wish, Fan Ko goes to Thailand to seek his half-brother Wun Li.
Wun Li is in trouble. He's a good fighter who hates gamblers, but the gamblers are trying hard to rope him in. As part of their plan, they've matched him against The Killer, the national champion, two of whose opponents have died in the ring. Wun Li explains to his girl, Yu Lan, that he simply must win.