"The Summons" by A. E. W. Mason is a novel published in 1920. Set during the Great War, it follows Martin Hillyard, a secret service agent, and his friend Harry Luttrell, an army officer determined to restore his regiment's tarnished honor. Their parallel missions intertwine with romance, espionage, and tragedy when Luttrell falls for Joan Whitworth, who becomes entangled with a suspected German spy. A mysterious death threatens to destroy reputations and futures in this adventure drawn from Mason's own wartime experiences. (This is an automatically generated summary.)