Cass and Carl are eleven year-old twins. They spend most of their spare time in the local park near a grand old Moreton bay fig. The council is going to cut the tree down because of complaints from a wealthy resident. The twins try desperately to gather enough signatures on a petition to save the tree. Just when they lose all hope of getting enough signatures in time, they are drawn into the tree where they meet the guardian of the tree - the Trumpalar.