'I Spy' is an adventure-mystery novel written by Natalie Sumner Lincoln. The story is set in World War I, when the allied forces, English and French, had been bent backward day by day, until it seemed as if Paris was fairly within the Germans' grasp. Bent indeed, but never broken, and with the turning of the tide the Allied line had rushed forward, and France breathed again. Two men, seated in a room of the United Service Club in London one gloomy afternoon in November, 1914, talked over the situation in tones too low to reach other ears. The older man, Sir Percival Hargraves, had been bemoaning the fact that England seemed honeycombed by the German Secret Service, and his nephew, John Hargraves, an officer in uniform, was attempting to reassure him. It was a farewell meeting, for the young officer was returning to the front.