The plot revolves around a new design for a submarine for the military and thugs who want to steal those plans. The main villain is almost as adept at using disguises as is the Shadow. Burbank, Harry Vincent and Cliff Marsland are all agents of the Shadow that make an appearance in the story.
There's also a traitor involved and it's up to the Shadow to track the evil-doers down and prevent any other villains from getting hold of the sub's plans. Since the story was published in 1935, it's possible that the potential buyers of the sub plans could have been the Germans.
When it comes to pulp heroes there are 2 or 3 great standouts and the Shadow is one of those. The stories are fast paced and action filled. The mystery just adds to the excitement. With his army of agents to help the Shadow never lets you down for a great read. Highly recommended