Yuen Tak Wah (Andy Lau) has been practicing Taekwondo since he was a kid and becomes an expert at it with his best trick being the 720 Degree Whirlwind Kick. Wah later becomes a cop and uses his good skills to contribute in cracking cases which leads to the jealousy of Officer Cheung Yeung (Roy Cheung), the leader of the rival team. Cheung is also a Taekwondo expert who has a won a championship at the Hong Kong Police Force's Taekwondo Tournament.

A group of desperate kids, marginalized and violently out of control, are holed up in a squalid Hong Kong tenement. Cops are a dimly perceived alien force, to be avoided at all costs.

Drug lord Au Kai kills his man Li Tin-Kit after finding him as an undercover cop. Tin-Wah vows to avenge his elder brother, and he mixes himself in Au’s gang for collecting the proofs of his crime. The rival of Au, Sister Ha, takes advantage of the chance to make Tin-Wah kill Kan to weaken Au’s strength…