Eighteen-Word Puzzle Case

The novel "The Case of the Eighteen-Character Puzzle" tells the story of the male protagonist Tie Kou, a novelist and typesetting staff, who receives a strange email message that will change the lives of their group and Tie Kou himself. There are also some social network reports that lead to a murder mystery. The case was seriously involved in his life, and even linked to the safety of his friends and family. Tie Kou had to discuss with his friends and search for the answer to this riddle alone. In order to find the real murderer, he could reverse his own destiny. And deep down, what do those 18 characters represent at the same time?