Nick Cheung plays a cop who's been undercover in a gang for 8 years before busting his boss, Francis Ng. Now he's back on the police force and no one trusts him.

Hong Kong police movies have been pretty rampant over the past half century. With the release of the blockbuster "Infernal Affairs" in 2002, Hong Kong police movies have been smarting up in terms of story line and plot twists.

Cinematographer cum director Herman Yau is at the reigns of Hong Kong's latest police drama which stars Nick Cheung ("Election"), Francis Ng ("Infernal Affairs 2", "Gen X Cops"), Rain Li ("Goodbye Mr. Cool") and Anthony Wong ("Initial D", "Infernal Affairs"). It tells the story of young cop Harry (Cheung) who is assigned to go undercover for the triads for the past 8 years (his entire career) where he is to gain confidence of the mob and gather evidence against the head honcho Don Dark (Ng). The movie explores the human element, which sees the emotional side of a person who lives a lie and actually becomes one of the bad guys whom he is trying to bring down.

The film is told in a series of flashbacks, and this is done nicely. It begins with Harry finally taking in his 'boss' Don Dark after sticking with the triad for four years. Needless to say, after the initial arrest, Don Dark's boys are all in a ruckus over the mole that they put their trust in. However, things are not so rosy on Harry's side as well, as he feels unaccepted by the police force and is constantly being tailed by the IIO (Internal Investigations Organisation). He is also left out of police briefings. Being with the triad for so long, Harry feels confused about where he really belongs.

The acting skill of Nick Cheung is what makes this movie get above par. His portrayal as the lost and brooding cop Harry is believable. Veterans Anthony Wong and Francis Ng are also great in their respective roles, although Wong seems a little misplaced but worked his magic as an arrogant field officer (we usually see him as a Superintendent). Rain Li plays Harry's love interest who works in karaoke lounges and is the eye candy of the film.

Running at about 90 minutes, this film would actually fare better if it were at least thirty minutes longer. Reminiscent of "Infernal Affairs", the film has the potential to cover a lot more ground on its characters and story.

If you like crime movies that are story-driven and gripping, then watch "On The Edge". You won't be disappointed.