I Spy - Illustrated

I Spy is a story about a WWI German spy plot to steal two American inventions deemed of inestimable value for war use. One is a camera for taking a map of the country from an airship. The other is a process for making glass armor—coats of mail of interwoven mica and glass that rifle bullets cannot penetrate. Washington DC is the locale. Almost everybody turns out to be a bit of a spy and the last unraveling chapter certainly carries the element of complete surprise (NY Times).