连环命案、私刑执法、预告杀人、以暴制暴...一群号称“神探”的团伙掀起了一场香港有史以来最邪恶的犯罪！患有精神疾病的“癫佬神探”李俊（刘青云 饰）为查真凶独闯犯罪现场！以“神探夫妇”陈仪（蔡卓妍 饰）和方礼信（林峯 饰）为首的重案组也开启了与杀戮赛跑的缉凶之路！敌友之间，正邪边缘，死亡审判的真相究竟是什么？真正的“神探”到底是谁？When Hong Kong is rocked by multiple gruesome murders, the police forms a task force to investigate. Jun (Sean Lau), 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.