Italy and the United Kingdom have just signed a naval treaty and France and Russia will pay anything to know the latest British naval plans, some of which must be contained therein. While it is being copied at the Foreign Office, an audacious thief acts. The disgraced official, in whose care the original was trusted, loses his mind and then, months later, calls in Sherlock Holmes because the treaty, surprisingly, is still secret. Can the famous detective save the day?
