This story about assassins takes place in a fanciful world. Yim Mo (Wayne Lai), who used to have a prestigious nickname "Yama", has caused his family to break up with fatal consequences due to his blunder. He ends up as a mediocre killer. He has facilitated the emergence of a formidable hitman called Kiu Sing (Moses Chan), aka "Zero". However, the duo's destinies are rewritten because of a Taiwanese tycoon called Or Ching-hung. Yim Mo counts himself lucky as his buddy Yiu Suk-han (Elena Kong), who is a hooker by profession, manages to bridge the communication gap between him and his daughter Yim So-chi (Louisa Mak). Unfortunately, Yim Mo's life has become very difficult as an eccentric female assassin called Yik Lan (Katy Kung) keeps clinging to him. Kiu Sing opens a cafe as a decoy and hires a single mother called Chin Heung-sin (Ali Lee). He also has a crush on Lam Sum-sum (Samantha Ko), who is a temple keeper with a mysterious background. Yim Mo and Kiu Sing are forced to engage each other in a duel as Assassin Hunter shows up.