The Case of Her Majesty's Secret Mission - The New Adventures of Sherlock Holmes, Episode 15 (Unabridged)
Description of book
There is a mole hiding in the British Embassy in Brussels. Important secret papers regarding the colonial politics have been stolen. In order to keep a diplomatic and international crisis from happening Holmes and Watson travel, of course incognito, to Belgium. There they want to put a stop to the traitor's game.