In Cue for Treason by Geoffrey Trease Peter and Kit are both running away from Sir Phillip Morton of Cumberland, England, and they meet up in an acting troupe headed by the Desmonds. Their meeting soon leads to a fist fight during which Peter discovers that Kit is really Katherine. Peter is running from Sir Phillip because he had the misfortune of hitting Sir Phillip with a stone during a political protest. Kit is running from Sir Phillip because she was being forced to marry him; he wants her fortune.
When Peter and Kit get to London, with out Desmond who injured his led, they are taken on by William Shakespeare as apprentices. Now the intrigue starts. Peter see a man working for Sir Phillip steal one of Shakespeare's scripts and acts courageously to steal it back. While doing so, Peter overhears a terrible plan to murder Queen Elizabeth I. Peter rushes to the head of the Queen's Secret Service and them he and Kit are sent undercover to learn the details of the plot to murder the Queen.
After being captured and escaping, Peter and Kit rush back to London with the secret of a planned new regime for England after the Queen is murdered. Encountering Desmond and the troupe on the road, Peter enlists them in capturing Sir Phillip. Peter and Kit resume their mad dash for London and in just the nick of time the Queen's guards capture the villainous John Somers moments before he pulls the trigger on the Queen. All is well because of the intelligence, determination, courage, foresight, daring, wisdom, quick wits and strength of Peter and Kit, who marry and live in peace in Cumberland.