Ahead of the German Blitz during World War II, English parents from every social class sent their children to the countryside for safety, displacing more than three million young offspring. In The Secret Guests, the British royal family takes this evacuation a step further, secretly moving the princesses out of England entirely, to the estate of the Duke of Edenmore in "neutral" Ireland. A female English secret agent, Miss Celia Nashe, and a young Irish detective, Garda Strafford, are assigned to watch over "Ellen" and "Mary" at Clonmillis Hall. But the Irish stable hand, the housemaid, the formidable housekeeper, the Duke himself, and other Irish townspeople, some of whom lost family to English gunshots during the War of Independence, go freely about their business in and around the great house. Soon suspicions about the guests' true identities percolate, a dangerous boredom sets in for the princesses, and, within and without the Clonmillis acreage, passions as well as stakes rise.