Chen Hu (played by Shi Xiaolong), who has just been appointed as the captain of the Shanghai Police, receives a murder case. The deceased, He Manjun (played by Bai Long), is the son of an important member of the Military and Political Department of the Shanghai Government and a student of St. Martin's High School. In order to obtain first-hand information to solve the case, Chen Hu has to disguise himself as a student and sneak into the school. Chen Hu, who is not good at studying, is miserable in high school study and life. He often makes a fool of himself and becomes a laughing stock. At the same time, he investigates the case while competing with various forces. The death of He Manjun is shrouded in mystery. Suspects appear and are eliminated one after another. What is the truth of the murder and who is the real murderer?