Three years ago, there was a murder in pinghai city. in the process of capturing the suspect cao ming, the criminal police chief ding wei sacrificed heroically to protect the hostage. after three years, similar cases were again staged. for this reason, the pinghai municipal public security bureau decided to transfer the backbone of the criminal police detachment: xu zhixin, the criminal police chief; liu jing, a criminal psychologist; luo hai, the detective expert and deputy captain; physical and biochemical materials dr. lin xue, a young female policewoman, and a female fighter, hu niu, who is a good fighter in the battle; wang xiaobo, a computer network expert, formed a large criminal detachment of the criminal police detachment, responsible for the detective tasks of such cases. liu jing and his colleagues used their own specialties in the process of detecting the case, and analyzed and speculated the motive of the crime through role-playing and description of the suspects involved in the case.