When Sash is forced to move from his comprehensive school in Peterborough to a private school in London he feels like an outcast. His taxidermist father, Max, is too busy to notice, absorbed in his secret life.

Sash finds a riddle in his father's study that changes his life forever. Max is searching for a legendary bird of flames, rumoured to bind enemies in friendship. Sash resolves to find it first. Verity, the most popular girl in the school, insists on helping, on one condition: no one must know of their secret alliance. Together they discover the entrance to the Fleet, London's largest underground river and find a portal to Aqarti - the tropical homeland of the mythical bird of flames. But beneath the suns of a dazzling new world, dangerous forces are also at work. Soon Sash and Verity are in a race against time to find the bird and decide its fate, before returning to this world to face their own futures.