During the time Hong Kong was under British rule, there was a dark age when corruption and bribery were the order of the day.

Chinese Chief Sergeant Lak (Tony Leung Ka-fai) together with his gang, Unicorn (Anthony Wong), Gale (Eason Chan) and Gold (Wong Jing) laundered massive sums thereby making Hong Kong an empire of graft.

Whenever they failed to apprehend the felons, Unicorn would get innocent victims, like Bong (Alex Fong), to admit to the crimes.

Only Lily (Kate Tsui) was loyal to him, but Gale was fascinated by the female drug lord, Rose (Liu Yang).

In the early 1970s, the Governor of Hong Kong decided to clean up the police force.