Han Qing (played by Sun Li), a female police officer of the Sanhe Criminal Investigation Team, secretly continued to investigate her whereabouts after her tacit partner Zhong Wei (played by Luo Jin), who had worked with her for many years, disappeared mysteriously.With the emergence of a new murder case and the joining of trainee police officer Lin Jiajia (played by Ding Guansen), she discovered from clues that the murder case was related to Zhong Wei's disappearance.But in the process of handling the case, criminals can always be one step ahead. They suspect that it was a % of insiders in the police station... After a series of criminal incidents and confusing cases, can they overcome the darkness and find the truth behind it?