Readers first met Lord Walter FitzGibbon in the book ‘Lord Compton’s Folly’. Now, several months later and with the death of a fellow espionage agent on his conscience, he has left the Admiralty’s service. Gorman, the agent, had been killed trying to prove or disprove a rumour that a French plot existed to assassinate an important but unknown British personage. The Admiralty, however, has not forgotten FitzGibbon. He is offered the chance to investigate the rumour further. He hesitates; a lovely young lady, Franny Bowman, has caught his eye and interest. But she has left London, and the chance to perhaps avenge Gorman is too tempting. He accepts the mission.
As Henri Langois, a fictitious relative of a French nobleman, he visits Elden Park, the country home of John Delaney, a wealthy, self-made man with strong ties to France. . FitzGibbon is welcomed and accepted by the host and his guests, but his heart nearly stops when he meets Delaney’s daughter, Jannette. She has seen him just before Gorman was killed, when FitzGibbon was disguised as Gascoyne de Verre. If she recognizes him, his mission, perhaps his life, is in jeopardy.
Jannette is sure they have met, but cannot place him. She says nothing to her father, but Henri politely avoids her. She dislikes and suspects him, yet is attracted too. FitzGibbon finds himself more and more interested in the intelligent, well-educated and beautiful Jannette, but she, her family, and their guests may all be traitors, bent on treason. Until he discovers their guilt or innocence, he must push his personal feelings aside.
The lovely house hides many secrets. Clues point in different directions. Although his life is threatened, FitzGibbon must play the charade to the bitter and deadly end. Time is running out; he must act quickly to avert disaster. Even a posthaste race to London may be in vain, but London is the final stage, amid pomp and ceremony, where an evil man plans to kill. FitzGibbon has to make a last-minute decision. An innocent life, as well as all he treasures, depends on his choice.