The talented female forensic doctor Gu Yu sneaked into the mental hospital to perform a disguised investigation mission. Unexpectedly, the undercover plan was destroyed by a homicide case, and she was almost framed as the murderer. Therefore, Gu Yu met the female criminal police Bai Lu. The two people's personalities are incompatible, and their living habits are also very different, but this magical combination has repeatedly solved strange cases. They have established a deep friendship from the initial mutual restraint to mutual empowerment. In the process of solving a criminal case by Gu Yu and Bai Lu, they accidentally discovered the traces of Gu Yu's missing brother. The disappearance of Gu Yu's brother is inextricably linked to the death of Bai Lu's boyfriend, all of which point to overseas drug-making gangs. The fate of the two is closely connected by the people they love deeply, and they have a common goal-to find the source of all evil. They firmly believe that there must be the truth under the traces.