A former police with a mental disorder works with an elite inspector in a series of murders seemingly connected to past cases. They find themselves in a race against time to find out the truth and the mastermind behind these murders.
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.
