The Royal Hong Kong Police Force is on the brink of executing a significant undercover operation aimed at apprehending crime lord Chu Tao. Among the team, Inspector Chan Ka Kui (or Kevin Chan in certain versions), portrayed by Jackie Chan, plays a crucial role. As the operation unfolds, tensions rise when the criminals spot the police, leading to a dramatic car chase through the hillside shanty town where Ka-Kui bravely pursues them on foot, determined to stop the drug lord, who attempts a getaway in a double-decker bus. Displaying his boldness, Ka-Kui manages to halt the vehicle by threatening the driver with his service revolver.
Although he later faces reprimand from Supt. Raymond Li for the chaos that ensued, he is subsequently paraded before the media as a hero of the police force. His next assignment is to safeguard Selina Fong, who is Chu Tao's secretary. In a clever move, Superintendent Li grants bail exclusively to Selina, insisting she speak with him privately, away from Chu’s legal counsel. This maneuver aims to create the illusion that she is willing to cooperate with the police in exchange for dropping the charges against her.
Initially reluctant to accept protection, Selina’s stance shifts when Ka-Kui stages a brazen act where a fellow officer breaks into her home disguised as an assassin. As fear sets in, she begins to cooperate with the police. However, the situation grows dire as Chu's lawyer persuades him to hire a hitman to eliminate Selina.
As fate would have it, the storyline takes a twist when Ka-Kui returns home to find his girlfriend May celebrating his birthday with friends. Tension escalates when May walks in on Selina clad only in lingerie and Ka-Kui's jacket, leading to a misunderstanding that angers her. Despite Ka-Kui's attempts to explain the situation, Selina's presence causes great embarrassment, prompting May to storm out, only to appear at Chu Tao's trial the following day.
In a surprising turn, Selina uncovers the truth behind the so-called attack on her apartment; it was all staged. Seizing the opportunity, she decides to erase her earlier confession regarding her ties to Chu Tao while Ka-Kui sleeps. This betrayal leads to her absence from the trial, resulting in a serious setback for the prosecution as they fail to secure a conviction due to her tampering.
With Chu Tao secured on bail and thirsting for revenge against Ka-Kui, he kidnaps Selina, threatening her life to ensure her silence. Unwilling to stand by, Ka-Kui launches a rescue mission, but he soon finds himself facing numerous henchmen. The plot thickens when Inspector Man reveals he’s been working with Chu, aiming to frame Ka-Kui for murder by having him kill Man with his own weapon. Now labeled a fugitive cop killer, Ka-Kui must navigate this treacherous path to uncover the truth and exonerate himself, even taking his superior hostage momentarily to evade capture.
As the climax approaches, Selina makes a bold move by infiltrating Chu Tao's office at a shopping mall with plans to download incriminating evidence from his computer. Unbeknownst to her, Chu and his thugs catch wind of her actions and rush to intercept. Meanwhile, Ka-Kui and May, who are surveilling Chu's movements, find themselves embroiled in the ensuing chaos. In a spectacular display of skill, Ka-Kui disposes of Chu's henchmen and wreaks havoc within the mall. In a dramatic showdown, the briefcase containing vital evidence slips to the ground floor, and although Chu attempts to reclaim it following an attack on May, Ka-Kui shrinks the distance, descending a pole adorned with light bulbs to confront him.
However, as the police arrive in droves, Ka-Kui is restrained from further action. In a tense moment, Selina courageously steps forward, asserting that it was Danny who murdered Inspector Man and attesting to the evidence contained in the briefcase. The arrival of Chu's defense attorney stirs further tensions, leading to a barrage of physical confrontations as an exasperated Ka-Kui confronts both the attorney and Chu in a dramatic, albeit chaotic, culmination of this electrifying tale.
