Fallon Chu (Donnie Yen) is a Hong Kong Police Special Task Force agent. An agile fighter with a high crime detection rate, he's considered a role-model in the eye of both the police force as well as the public. He gets assigned to a case of escorting a well known criminal to Japan using his experiences and fighting capabilities to keep it safe during the job. Unfortunately, things are not going well in his private life as he has to deal with problems with his fiancee while planning their wedding. After a series of mishaps between them, she suddenly dumps him. Heartbroken he indulges himself in food to relieve his state of shock and loneliness, and in three month' time his endless intemperance turns him into a 300-pound being.