Tang Ze's mother was killed on her duty three years ago by a drug dealer in order to avenge Yan Xue's father, who died in order to save Tang Ze's mother, leaving Yan Xue fostered in Tang Ze's family.Later, Tang Ze became a member of the Criminal Investigation Bureau and engaged in special intelligence work; After graduation,Yan Xue found Tang Ze, whom she hadn't met for three years. and joined the Criminal Investigation Bureau under the persuasion of her colleagues. The two of Yan and Tang worked together and solved a number of cases, during which their feelings towards each other were quietly changing. In order to find the drug dealer who killed his parents, Tang Ze lurked in the drug trafficking gang to find the clues of that year, while Yan Xue was helping Tang Ze and the police to investigate for the truth in her own way, but to be shocked by Tang Ze's action when the truth came.