The German Navy Changes Its Code
Adventure #2 in the collection . First published in Thomson's Weekly News 09/10/1918 and syndicated to the Glasgow Sunday Post, 09/15/1918.
On one of his clandestine trips into Germany, John Frazer got an inkling there might have been a change in Germany's main military code. Returning to England, he confirms it so it is now up to him to go back to Germany and find a way to get a look at the new cipher.