Yan Yan lost his mother when he was young and lived with his father. He is sensible and obedient, and he also tries his best to restrain himself from a woman who lives with him, who has a hot temper and often neglects his father. In the end, an ordinary dispute led to an extreme incident, and his father left him forever. Yan Yan, who had no guardian, was sent to live with a distant relative, where he met Xin Yue, who was in the same situation. When Yan Yan was ridiculed by almost every classmate, Xin Yue chose to stand by his side. This move made Yan Yan remember it in his heart. The short-lived friendship ended due to a premeditated attempt by a malicious classmate. Then he discovered something even more sordid. At this point, he was forced to stay away from this place. More than ten years later, it was not until a fall occurred in the Chengshangcheng Building that Yan Yan came closer to the police's attention. He has always been by Xin Yue's side to protect her in another way. As the case progressed, the police found several other murder cases that were closely related to this case, and finally identified Yan Yan as a suspect, and he chose to die to apologize.
Purpose: With the development of society, people's views on marriage have begun to change significantly. There are more and more single-parent families, and some children have embarked on different life paths because they lack the care of their original families. The book starts from this point. The murderer also lives in a single-parent family. Through the development and progression of the case, he reviews the tragic situation of his childhood in the process of revealing the murderer. Even so, he keeps a promise that seems to be a joke, allowing readers to view the problem in two while condemning the crime.