Lady Drusilla Davanish, summoned to 10 Downing Street by William Pitt, is warned that John Hamerton, soon to be her guest on the Isle of Wight, may be a top French spy. Hamerton's brother-in-law is close to Robespierre, the most feared man in France. But is Hamerton a traitor? Is this bluff, typically English gentleman really behind a plot to shoot the King and start a French style revolution in Britain? Drusilla, given the task of uncovering the truth, risks her life to save the King and discovers the man she loves is hiding the biggest secret of all.