To keep his chief source of income from drying up, corrupt customs agent Prince Mu ((Wong Kam-kong) decides to snuff the official charged with enforcing a Chinese government edict banning the opium trade. Enter martial-arts champ Sam the "Iron Bridge" (Do Siu Chun) to safeguard the officer tasked with ridding China of the drug. But Sam's involvement soon becomes complicated by his approaching nuptials and his growing feelings for Mu's daughter.