Which high-IQ crime novels are Chinese works?

It should be a novel from before 2014. It was first published on the Internet. The main story was about a little boy whose parents were divorced and lived with his mother. He seemed to be a junior high school student. Once, he went hiking with his two friends (brother and sister, who grew up in an orphanage). They accidentally bumped into a man who pushed his parents-in-law off a cliff and accidentally recorded the video. Later, he used this matter to threaten the man. The man planned to kill the three children. In the end, the two friends of the little boy died and the little boy escaped. The little boy was a very intelligent child, and he used a holiday journal to cover up other things (like crimes). The man who killed his parents-in-law was a phoenix man. His wife didn't like him, but she married him because her parents liked him. Unexpectedly, she found out that this man was very scheming and wanted a divorce. The man wanted the woman's family's assets, so he killed his parents-in-law. The novel also talked about some other plots related to little boys. I can't remember clearly. Does anyone know the name of this novel?