Kumer So

When Hong Kong is rocked by multiple gruesome murders, the police forms a task force to investigate. Jun, once a brilliant detective who suffered a mental breakdown, begins his own investigation. Eventually, the police learn that the murder victims are all suspects of cold cases being rubbed out by a figure known as "The Sleuth". Now, Jun and a detective from the task force are on a race against time to beat the brutal killer at its own game.

Hong Kong police agent Cheung (by Aaron Kwok) works undercover in Kang’s (by Sean Lau) drug cartel, while another undercover cop Au (by Louis Koo) successfully earns their trust in an incident, a brotherly-bond is built among the three. After the Police busts the syndicate in Hong Kong, Kang subsequently hides away in the Golden Triangle, by chance he receives a tip-off about the betrayal within his circle of trust…