When Jennings' new diary is made public, the thought of his most private thoughts being made public spur him to invent a secret language. Will anyone be able to decode it? And how does Jennings end up on the wrong side of the law? And what of the collection of ancient relics a visit to the Natural History Museum inspires Jennings and Darbishire to establish? Find answers to these and other questions, in this entertaining story by Anthony Buckeridge, narrated by the award winning Simon Vance.