In 1924 Shanghai, there is a young, meticulous police detective named Fan Ruyi. He is determined to maintain law and order in Shanghai French Concession. Fan has always been cavorting with rascal characters in order to receive more intelligence for case investigation. He has then earned his boss' trust and is summoned for a secret mission, however, relentless misfortunate events then follows. A warlord's daughter Song Xiaoqiao is kidnapped… Fan's teenaged informant disappears… Fan's fellow colleagues and a student who studies in a prestigious school are also being killed. As Fan abruptly tries to stop these peculiar murders but out of the blue, he suddenly becomes the most wanted suspect among these cases.