Definitely not a popular story and perhaps hard to find in some cases, but DEFINITELY worth reading. This was made into a movie serial in 1920 starring Harry Houdini and reading it you get the feeling that this role of Quentin Locke of the Department of Justice was written specifically for Houdini with all his death defying feats in the story. Spies, poison gas, automatons, guns, women in peril, this story has everything, I definitely recommend it.