Mumble is originally a member of SDU, but once during a mission, Mumble was late reporting because he was chasing girls, his superior Kei Sir suspended him and forced him out of SDU. Mob boss Chiu Sai Bat doesn't like the mob's internal struggle affecting his daughter Ah Shuet, so he hires Mumble to protect her. Shuet doesn't want her father to continue dwelling among the underworld, so she causes trouble outside hoping to force her father to wash his hands clean. The mob's second in charge Uncle Yee wants to kill Shuet's father and to take his place. Mumble retreats from Wai Heung who constantly wants to kill him..