Ray Lui produced and starred in this rather tepid crime drama which has some nice touches and thoughtful exposition, but otherwise is not more than an average time killer. Lui is the head of a group of undercover cops, consisting of Simon Lui (who also co-wrote the script), Mark Cheng and Wong Hei. The four are bound for Malaysia to search for missing cop Daniel Wu, who went on an undercover assignment and has since gone missing. Worst case scenario: he's dead. Even worse case scenario: he's gone evil and become a drug-running bastard. Some of the cops believe that Wu has gone turncoat, while others think he's innocent. Lui, in particular, has a personal stake since he was Wu's mentor and buddy.
     The standard details of the cops' lives and mission take up the majority of the screen time, with much exposition reserved for soul-searching regarding cop corruption and "undercover blues", i.e. how being an undercover cop sucks. The mismatched group of cops make for some amusement, but they don't take on much personality, unlike the Milky Way productions Expect the Unexpected or The Mission. Part of this could be the fault of the actors, who range from decent to just-plain bad. Or, the script could be at fault, as it spends too much time with tell rather than show. Director Billy Chung keeps things moving at a decent pace, and the climax of the film certainly settles things. However, despite a reasonably decent production and a minor foray into darkness, Undercover Blues doesn't register as more than a mildly interesting genre exercise. The film lacks the requisite energy or panache to take it to another level. As it is, it exists lamely, like a crippled dog. (Kozo 2000)