A criminal psychologist and a forensic expert works together to track down a serial killer who targets people who have been acquitted of notable crimes and uses their guilt as his modus operandi.

Set in the late Ming Dynasty, “Brotherhood of Blades” tells of three close friends who serve as Jinyiwei guards. They are dispatched by a palace eunuch (Nie Yuan) to hunt down Wei Zhongxian, a eunuch politician who had been forced to resign from his influential post and exiled from Beijing. The Jinyiwei brothers return successfully from their quest, only to find that their task was but the beginning of a strange conspiracy.

A lonely young man (Haruma Miura) happens to meet RuoLan who has an identical twin sister RuMei. They are older than him. RuoLan tells him about her wound from a painful breakup and her troubles being a twin. While supporting RuoLan, the young man gets close to her.

When a spate of eerie murders erupts across HK two troub/emaking cops are assigned to the case. Young maverick Wang and grizzled vet Huang who is fed up with his reckless younger partner always landing them in hot water. Reaching a dead end after discovering all the victims were former boyfriends of aspiring starlet Liu, the detectives must play a deadly game. One of them must go undercover as Liu’s lover to lure the killer out.