In Agatha Christie’s short story, “The Submarine Plans,” Poirot is summoned to the home of Lord Alloway, head of the Ministry of Defense, to investigate the theft of top-secret plans for a new submarine. With the First Sea Lord and his wife, and a mysterious Mrs. Conroy all staying the night, the suspects are numerous. This short story originally appeared in the November 7, 1923 issue of The Sketch magazine.