Through the clue of a coin, it reveals the truth of the mystery of the secret room, and points out the suspect of theft and kidnapping. Ouyang and Oumuqi, two highly intelligent teenagers, quickly solved the case through observation and scientific knowledge. Ouyang admitted that his previous suspicion of the security guard was wrong, while Oumuqi believed that Ouyang's inference about the "smiling face" sticker was correct. Mai Jie and Pi Xiaodong found the suspect abandoning the car and escaping near the station, speculating that the suspect may have used a wheelchair and the station's automatic car wash as cover. They further analyzed and believed that the suspect may have disguised himself as a train attendant and used the convenience of the station to carry out criminal activities. The whole chapter shows the intelligence and reasoning ability of detectives, and also describes the cunning and criminal tactics of suspect.

10、 Children's Theater

Mai Jie identified high-speed rail attendant Ning Jie as a suspect through investigation, as Ning Jie had committed the crime and exhibited abnormal behavior. Mai Jie and railway police attempted to board the train to arrest, but the train had already closed its doors and was about to depart.