Young middle school student Xiang Li Xiqi dreams of becoming a detective. Displaying a strong sense of deduction, he is determined to investigate the theft of his classmate Chen Jiayi's research paper. With the help of his friend and assistant Ren Shirou, no clue escapes his keen eye. After questioning the students, they discover that Li Jianan, Wu Mingdong and others had entered and left the classroom several times before Chen Jiayi's papers disappeared. What does their story have to do with stealing? Will Xiang Li Xiqi, faced with the doubts of his comrades, be able to find the culprit?