Shanghai is a place with many foreign concessions, evildoers, rich people and fools, and vanity and crime coexist. Therefore, it is called "Adventurer's Paradise" or "Magic City". As the smartest "investigator" in the concession, Fan Ruyi (played by Ethan Ruan) has to deal with all kinds of people every day, and obtain all kinds of investigation information from them, which makes him trusted by his boss. But one day, after taking over a top-secret task assigned by his boss, all kinds of unexpected and bizarre events followed: Song Xiaoqiao (played by Yang Zishan), the daughter of a warlord, was kidnapped, the young boy Xiaoliu died tragically on the street, female students from aristocratic schools, colleagues from the patrol room, etc. were all involved and none of them were spared. Fan Ruyi tried to prevent innocent people from being killed, but the result was beyond his expectation. The "number one suspect" of all the murders turned out to be himself! In order to clear his name, Fan Ruyi tries his best to avoid the pursuit from the underworld, the police station and the mysterious killer, and to protect the newsboy Xiaohou and the blind girl Huilan (played by Zhou Dongyu). He is willing to sacrifice his life and finally gets closer to the truth. However, the truth is much crueler than he imagined...