The Mysterious Numbers of Father and Son Detective

The University of Edinburgh, located in the French Concession, dug up two corpses while digging a well in the southeast corner of the campus. After hearing the news, Detective Chen from the patrol room showed up at the scene with his son Tiansheng. Based on the structure of the corpse, Tiansheng preliminarily concluded that the deceased was a man and a woman. When identifying the watches, earrings, and rings found at the corpse scene, forensic doctor Han Ling discovered with horror and pain that the woman among the deceased was actually her mother Song Min, who disappeared suddenly ten years ago, and the other male deceased was probably her mother's colleague Liang Zhongping. The ingenious and horrifying discovery plunged Han Ling into painful memories: Ten years ago, on December 17, 1921, her mother and her colleague Liang Zhongping went on a business trip to Beijing, and there was no news from them since. Looking for clues from Han Ling's memories, Detective Chen and his son Tiansheng came to visit Liang Zhongping's widow Zhou Xinmei. Since her husband Liang Zhongping disappeared, the school arranged for Zhou Xinmei to take charge of the school library with her somewhat mentally abnormal son Liang Yuan. Visiting Zhou Xinmei, Tiansheng not only learned that Song Min, Liang Zhongping, and Wang Shijie had studied under Song Min's husband Han Daren as three professors in the school ten years ago, and had been engaged in scientific research for a long time, but also found that Liang Yuan, who was mentally ill, was particularly sensitive to numbers, especially numbers such as 1921 1217...