In the 1930s, Guangdong Province was a city of mixed people. Lin Hao, the chief instructor of the mysterious organization "Black Front", faked his death during a mission to escape the control of the organization. He hid in the Wu Family Clinic on the outskirts of the city as a doctor, preparing to start a new life, but various circumstances dragged him into the center of the vortex again. While practicing medicine, Lin Hao met the rebellious new policewoman He Xinxin, and his identity also aroused He Xinxin's suspicion. As various cases in Huacheng occur simultaneously, Lin Hao and He Xinxin's relationship becomes closer and closer. Their feelings grow stronger as they test each other. The connections between the various cases they handle all point to a plague injustice case caused by a conspiracy 20 years ago. The mystery of Lin Hao's life experience is also hidden in it, and the truth is about to be revealed... Lin Hao decides to stand up again and joins hands with his girlfriend He Xinxin, the head of Huacheng Chamber of Commerce Zhuang Yu, the young doctor Zeng Fan who returned from overseas, the cold and outstanding female killer Leng Yuehan, and the clinic nurse Wu Ruolan to explore the truth together. However, the opponent is always hidden behind them, with strong power, like a black hole that wants to drag them into the abyss...