Hugh Thomson, a surgeon-major, is engaged to Geraldine Conyers. He is ostensibly in command of military hospitals on the French front, but in reality, he is the head of military counter-intelligence. He is on the trail of a German master spy who appears to be able to go across borders and between Germany and England. Captain Granet is a wounded war hero who was recently awarded the DSO and is recovering after being caught and escaping from the Germans twice. He meets Geraldine Conyers and falls in love with her. This novel was first published in 1916, during the early years of World War 1. It relates the thoughts and feelings of the upper class in London during the early stages of the war with astonishing dexterity.