The film tells of a well-intentioned narcotics agent, Nick (Daniel Wu) deep undercover in the heart of Hong Kong’s lucrative heroin trade. He is forced to deal with the hypocrisy and despair in a life of drugs and crime, as he plays protege to one of the key players of the game, “Banker” (Andy Lau). In the eight years he has been infiltrating the heroin industry, he finds himself corrupted by the easy money and his new found power. Unable to separate himself from his undercover persona, he immerses himself into his role as a drug trafficker.