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. After repeated visits and investigations, due to the limitations of criminal investigation technology at the time, the failure to lock the suspect's case became an unsolved case. However, the physical evidence testing in a murder case 13 years later brought the serial murder case 13 years ago to the surface again. The two criminal police officers who investigated the case that year once again joined forces for an inspection. After the hard work of a number of veteran criminal police officers, the real murderer was finally found and brought to justice, so that justice was done. Adapted from the novel “The Light of the Dark Night” (黯夜之光) by Lou Xiao Peng (娄霄鹏).