Badges of Fury (2013)

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.

Original title: 不二神探 (2013)