Ka, the time-travelling cat, has disappeared, leaving just one clue. Topher soon realises that she has gone back to Elizabethan England, and he fears that Ka is in terrible danger. In doing so, he meets Queen Elizabeth and Doctor Dee, the court magician and astronomer, who thinks Ka can help him find the elusive Philosopher's Stone.

Julia Jarman has written over 80 books for children. She lives near Bedford with her husband and has three grown-up children. She has been a schoolteacher and journalist but she now devotes a lot of time to school and library visits to talk to children about writing.