Little Kai (Sun Ya-Tung) is a member of a criminal organisation. The tattoo on his chest earns him the nickname of ‘Leopard’. Immediately upon Little Kai’s release from jail, his brother is framed and murdered. Suspecting that it’s an inside job, Kai returns to the organisation to see if he can find out root out who is behind his brother’s death.

Black Butterfly tells the story of a female assassin who is sent to Taiwan to clear the way so a gang from Hong Kong can take over the territory. Problems arise when she breaks the cardinal rule of an assassin -- never develop friends -- and she cannot complete the job. Now hunted by both camps, the killer must turn into a savior as she tries to help her friends.