Will his first case be his last?
Detective Dee Ren Jie (Mark Chao) arrives in the capital city of Luoyang to work as an officer of the law, known as the Da Lisi. A sea monster has been terrorizing the town, and city officials have chosen the most beautiful courtesan, Yin Rui Ji (Angelababy), to be offered as a sacrifice to the sea monster. Empress Wu Ze Tian (Carina Lau) demands that Yu Chi Zhen Jin (Feng Shao Feng), the Chief Minister of Da Lisi, investigate the sea monster or he himself will be executed.
When Detective Dee saves Rui Ji from being sacrificed to the sea monster, he is imprisoned by Yu Chi. Sha Tuo Zhong (Lin Geng Xin), the prison doctor, helps Dee escape from prison and investigate the mysterious sea monster.
When the sea monster is somehow tied to Yuan Zhen (Kim Bum), Rui Ji’s lover, can the two lovers help Detective Dee uncover the sinister conspiracy that leads straight to the Imperial family?