This suspenseful, entertaining, and wonderfully well-executed historical thriller imagines that in 1940, during the London Blitz, Princesses Elizabeth and Margaret are whisked away to a distant relative's crumbling Irish estate. Under the care of a female MI5 agent and a young Irish detective, the sisters—the elder prim and serious, the younger brash and precocious—grow increasingly bored with their sequestered lives. But as the staff and townspeople begin to speculate about the identity of the newcomers, fragile British-Irish relations and heightened wartime passions make keeping the girls safe an action-packed high-stakes adventure.