Step back. Dido is coming. Her name is Dido. Her name is also a star, Dido 209. Her grandfather, who was an astronomer, says so. When she grows up, she wants to become a wildlife photographer. This year she is in third grade, while Chu, her brother, is in fifth grade. On the first day of school, the principal talked about the black book. Any child who misbehaves one, two, three times will be entered into the black book. No one knows what the black book is. But it certainly sounds very scary. When Dido makes her third mischief and disappears, Chu organizes a rescue mission. Maybe then they will discover the mystery. Maybe they will realize that not everything is as it seems. And then they will dare to fight against injustice and darkness, wherever it hides.