A schoolgirl--Siu-Man--has committed suicide, leaping from her twenty-second floor window to the pavement below. Siu-Man is an orphan and the librarian older sister who's been raising her refuses to believe there was no foul play--nothing seemed amiss. She contacts a man known only as N.--a hacker, and an expert in cybersecurity and manipulating human behavior. But can Nga-Yee interest him sufficiently to take her case, and can she afford it if he says yes?
What follows is a cat and mouse game through the city of Hong Kong and its digital underground, especially an online gossip platform, where someone has been slandering Siu-Man. The novel is also populated by a man harassing girls on mass transit; high school kids, with their competing agendas and social dramas; a Hong Kong digital company courting an American venture capitalist; and the Triads, market women and noodle shop proprietors who frequent N.'s neighborhood of Sai Wan. In the end it all comes together to tell us who caused Siu-Man's death and why, and to ask, in a world where online and offline dialogue has increasingly forgotten about the real people on the other end, what the proper punishment is.