The Hong Kong Police Force is planning a major Undercover operation sting to arrest crime lord Chu Tao (Chor Yuen). Inspector Chan Ka-Kui (or Kevin Chan in some versions) is part of the operation, along with undercover officers stationed in a shanty town. However, the Crime spot the officers and the shootout ensues between the two groups in which civilians either flee the town or caught in the crossfire as a result of the gunfight. Chu Tao and his men successfully flee in their car by driving through the town but crashes it immediately after going downhill and escapes on foot. Ka-Kui persists in his chase on foot as Chu Tao and his men attempt to escape in a double-decker bus. Ka-Kui manages to get in front of the bus and bring it to a halt by threatening to shoot the driver with his service pistol.