Fourteen-year-old Madeleine Tully has run away from home with her mother. They are now living in an attic in Cambridge, but Madeleine knows it's just until her father forgives her and takes them back home. In the meantime, she is being home-schooled with her new friends Jack and Bella. When she finds a peculiar letter in a parking metre, she begins a strange correspondence with a boy who says he lives in another world. In the Kingdom of Cello, Elliot Baranski knows he is breaking the law by sending letters to the Girl in the World. But he needs someone to talk to about the truth behind his father's disappearance. Has he really run off with the teacher? Or was he taken by a Purple in a Colour Attack?