There's never a cop around when you need one. But when this cop's around, all you need is one.
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.
Inspector Chan Ka-kui has been demoted to highway patrol as the result of his handling of his previous case, which involved the violent arrest of crime lord Chu Tao and heavy property damage. The new duty pleases his girlfriend, May, who is glad that her boyfriend is no longer taking difficult cases and has more time to see her.
Ka-Kui is the "supercop" of the Hong Kong police, with amazing martial arts skills. He is sent to Guangzhou, where the Chinese police force's Interpol director, Inspector Jessica Yang (Michelle Yeoh), briefs him on his next assignment. The target is Chaibat, a drug lord based in Hong Kong. To infiltrate Chaibat's organization, Ka-Kui is to get close to Chaibat's henchman Panther, who is in a Chinese prison. Ka-Kui, posing as a petty criminal prisoner, manages Panther's escape with the connivance of the guards. Grateful Panther invites Ka-Kui to go with him to Hong Kong and join Chaibat's gang. Panther meets up with some of his other men, and vouches for Ka-Kui. The group heads for Hong Kong.
In the present day, a group of rebellious youths rob a bank with the intention of shooting police officers before making their escape. Inspector Chan Kwok-wing and his squad are called to arrest the gang after their hideout is revealed. However, the hideout is rigged with traps, and the entire squad is decimated. Being the sole survivor of the incident, a guilt-ridden Chan takes a year long leave from the police force to binge-drink.
夜幕降临，资深刑警钟文（成龙 饰）接到离家出走许久的女儿苗苗（景甜 饰）的电话，他暗怀喜悦准时来到了正进行三周年店庆的武吧。武吧老板武江（刘烨 饰）热情地接待了他，但是酒吧内光怪陆离和乌烟瘴气的景象让钟文心生不快。稍后，苗苗抵达，眼见得纹身染发并且桀骜不驯的女儿，钟文尽 量和颜悦色与女儿沟通，可当得知武江是女儿的男朋友时还是发了脾气。就在此时，一名民工为索要工钱带着炸弹入场，钟文出手不凡解决争端，可没过多久却被人用棒球棍打晕。 当他苏醒过来时，发现自己被人绑在椅子上，冷酷的武江宣布将其劫持为人质。有限的时间内，钟文不得不和这个狡猾凶狠的匪徒斗智斗勇，寻找逃脱的机会……
Hong Kong Special Agent Lin Dong was told that his daughter Xixi (who suffers from leukemia) is in critical condition. He speeds over to the hospital, but on the way his co-worker, Xiao Su, informs him that a critical witness is in danger. Agent Lin stops right outside the hospital, pauses, and turns back to protect the critical witness, Dr. James.