In the Line of Duty 4 (Yuen Wo Ping) - Cynthia Khan, Donnie Yen. [aka 'The Witness'. UK title: 'In the Line of Duty']
A variation on the theme of 'Yes, Madam', that of evidence ending up in the hands of someone who doesn't know it's worth. It begins in America, where a policeman taking pictures of a CIA endorsed drug deal is gunned down. Before dying, he passes the film onto an immigrant worker, who soon discovers a lot of people want it. After his brother is gunned down, he escapes to Hong Kong, pursued by Khan & Yen (a classic good-cop/bad-cop pairing), plus another policeman who is an undercover CIA agent.
This is a perfect example of the strengths and weaknesses of Hong Kong action films. The story looks like someone removed massive sections, as things suddenly happen without noticeable explanation. Fortunately, the action is incredible and virtually non-stop, so you don't notice the holes until about the third viewing. The highlights include Cynthia Khan demonstrating her prowess with nunchaku spanners (cut by the BBFC, naturally!), an ambulance battle where she out-Indianas Harrison Ford, and a final 10 minutes where everyone shows off their fighting skills, though these are only peaks in a distinctly high-altitude movie: given a better plot, this would have been the first kung-fu film to get A+, but A will have to do.