S1, E2: It tells the story of a series of serial homicides in Nandu, thirteen years ago. Wei Zheng Rong, an old policeman who is at the bottom of his life, led Lu Xing Zhi, a newcomer police officer who had just joined the job, to investigate the truth of the case. Due to the limitations of criminal investigation technology at the time, the failure to lock the suspect's case became an unsolved case.