Peter Brownrigg, a 14-year-old boy who lives in Cumberland in the north of England, is involved in a night crime against the theft of his village's farmland by Sir Philip Morton.

Kit is actually a girl in disguise, really called Katharine Russell, who is running away to avoid a forced marriage to Sir Philip, who is only interested in her inheritance.

After being initially turned away by Burbage, they are accepted as apprentices by the playwright William Shakespeare, who recognises Kit's acting ability and Peter's gift of mimicry.

Peter and Kit take the poem to the Queen's secret service who decode the poorly written sonnet, discovering that the first letter of each line spells SEND NEWS BY PEEL.

Tom is killed by the conspirators and Peter is captured but not before learning that John Somers, an actor in their company, is to shoot the Queen during the first performance of Henry V. This is part of a wider conspiracy to install a new regime in England, the rest of it is vague but they are evidently in league with Spain.

Knowing it is only a matter of time before Sir Philip realises his error and returns, the actors dress up in their soldier costumes and rig the horses to sound like an army ready to attack, with trumpets and drums behind.

Kit and Peter make a desperate dash back to London, and John Somers is captured by guards moments before he can shoot the Queen.

The novel is marked by a strong sense of place, particularly showing Trease's love of the Lake District, where he also set his Bannerdale stories, including No Boats on Bannermere.

The politics of the Elizabethan era are mentioned in the novel: social concerns over enclosures and unemployment, and the state matters of rebellion and invasion.

The motives of the conspirators are not examined, being assumed to be simply wealth and power; although historically religion would have been a factor, this is not mentioned beyond a casual reference to "old ways".

The English Renaissance theatre is represented by its two extremes: a poor temporary company which tours around England, and the Lord Chamberlain's Men who perform for the Queen and her court.