Jennings is suffering from beginning-of-term-it is, but things soon return to the normal state of mayhem when his new diary is made public property! Alarmed at the thought of his most private thoughts being made public. Jennings invents a secret language. Inspired by a visit to the Natural History Museum. Jennings and Darbishire establish their own collection of ancient relies, but they are not out of trouble for long and when the precious diary goes missing, Jennings finds himself on the wrong side of the law!