A Sunlit Weapon: The thrilling wartime mystery - Maisie Dobbs

Late September, 1942. Jo Hardy, a 22-year-old ferry pilot, is delivering a Spitfire to Biggin Hill Aerodrome when she realizes someone is shooting at her aircraft. When she returns to the location on foot, she finds an American serviceman in a barn, tied up and gagged. Jo hurries away, but can't shake the image of the serviceman from her mind.