On the moon night of the Mid-Autumn Festival, Chen Qiusheng is murdered in the home of tycoon Nie Chengjiang. He Kun, and two men saw a hand holding a knife in the mirror and stab Chen Qiusheng to death. The crime scene was locked in place and Qiao Chusheng, the patrol house inspector, found that there was no place for the killer to hide. The walls were solid and the ceiling had no windows. After the incident, there was no escape route from the scene. After the investigation, Lu Yao, a manager of SAXON Bank who had a dispute with the deceased, was listed as a top suspect and detained in the detention room.