While interpreting a deaf-mute murder case, Bai Mo discovered that the suspect's sign language narrative was mixed with an extremely ancient "taboo sign language system" that did not belong to him at all. Tracing the origin of this set of sign languages, she uncovered a society of voiceless people that had been passed down in the shadows of the city for hundreds of years. They used their fingertips to record the truth that had been erased from official history. The murder was an attempt to silence the "living history book".
