In this tale of espionage set during World War I Britain, we encounter a variety of characters. Surgeon-Major General Hugh Thomson, the works apparent antagonist, who is endeavoring to clear the British troops of spies. He is on the trail of a German master spy who seems to be able to travel across the lines and back and forth between Germany and England. Captain Granet is a wounded war hero recently awarded the DSO and recovering after having been captured twice and escaping twice from the Germans. From an encounter with Captain Ronald Granet at Granets aunts luncheon, Thomson begins to feel suspicion toward him. But is this only due to Granets interest in Thomsons girl, Geraldine Conyers?