A. E. W. Mason 
Summons 

The Summons is a 1920 novel of adventure and romance by A. E. W. Mason, published by Hodder & Stoughton. Set just before and during the Great War, the novel recounts the adventures of Martin Hillyard, a secret service agent, and his army officer friend Harry Luttrell who aims to restore the battered reputation of his regiment. Hillyard has been called the nearest approach to a self-portrait that Mason ever drew, and his childhood and secret service wartime experiences are based on those of the author himself.