Late at night, an anonymous message appears in the property owners' group chat for Building 3 of Lijing Apartments: Wherever the song "Drop the Handkerchief" ends, an owner will meet a death meant just for them. Don't chat in the group; the killer may be posing as an owner and hiding among you. When the nursery rhyme begins, the owner of Unit 2003 dies after posting in the chat. Their manner of death eerily echoes their earlier complaint about being kept awake by dripping water. Chen Mo and Lin Wan must use clues in the group chat to identify the killer and avoid falling victim when the song sounds again.
