A brilliant detective is forced into early retirement after losing eyesight. Making ends meet by solving cold cases for reward money, he teams up with a rookie lady inspector to solve a case from her personal past.
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.
Realising that he will be defeated in no time during a police showdown, a thug shoots himself to force the cops to cease fire and take him to the hospital. In the hospital, he claims human rights to refuse immediate treatment in order to buy time for his underlings to rescue him. The detective in charge sees through his scheme but decides to play along so as to capture his whole gang once and for all.
