London, 1892—Cyrus Barker is brought into a game of international espionage by the Prime Minister himself in the newest mystery in Will Thomas's beloved series.Private enquiry agents Cyrus Barker and Thomas Llewelyn receive in the mail an unexplained key stamped with the letter Q. Barker, recognizing it for what it is, uses the key to unlock an anonymous door in the alleyway, which opens to an underground tunnel leading to Downing Street.The Prime...