Death Notice

In Country A, I receive three letters every day. There is no sender or address, only a tiny grinning ghost face. The day after a letter arrives, someone dies, and the crime scene looks exactly like the photograph inside. Detective Wu Jian, an elite investigator, and I searched far and wide, eventually narrowing our suspects to the "Haunted House" on Khao San Road. But inside, we encountered something unclean, and another murder took place in the process.