The story takes place in Shanghai in the 1920s. Tang Lang (played by Huo Jianhua) has always been impartial in handling cases, so he offended his superiors. He had to leave the police station and open a detective agency alone to practice the conscience and justice that a detective should have. Gang leader Du Bailong (played by Kaohsiung) escaped from prison because he was sentenced to life imprisonment. He vowed to kill all his enemies and issued death threats to the judge Xie Tianhong (played by Huang Jue) who sentenced him. After taking over the case, Tang Lang made every effort to solve it. During the investigation, he found that the original verdict on Du Bailong was actually someone who lied about his guilt. It was a complete injustice. This discovery was extraordinary. At this time, Huang Que (played by Zhang Meng), a lawyer studying in the UK, received a mysterious commission to help Du Bailong overturn the case. Unexpectedly, Du Bailong disappeared for many days after escaping from prison, and Huang Que could not see the client at all. As Tang Lang and Huang Que discover the unspeakable secret in the Du case, they are hunted by evil forces at the same time. Although they are both working for justice and the law, their different worldviews reflect completely different life trajectories...