One of the few times that Sherlock Holmes' brother Mycroft is even a minor character in a mystery by Sir Arthur Conan Doyle. He asks Sherlock to help the empire get back secrete plans of a new technically advanced submarine before they are sold to a foreign power. This is a perfect example of the author's fine style of writing; it incorporates mystery, suspense, murder, deceit, and greed with Sherlock's unsurpassed analytical skills which of course saves the British Empire of serious consequences. If you have never tried one of the original Sherlock Holmes mysteries, this is an excellent story to start with. Highly recommended.