16th of 19 stories in the anthology My Best Spy Story, 1938. It was also included in the anthology The Big Book of Espionage edited by Otto Penzler in 2020.
The man known as Luss has trafficked in sensitive naval intelligence but has thus far managed to stay out of prison, largely because he changes his identity so often. When Colonel Ormiston is brought in to investigate the photographing of a new naval code by a spy posing as a window washer, the conflict between Ormiston and Luss goes into high gear.