Thomas Howard of Missouri came out of nowhere, one foggy night, to rescue Countess Elaina Montague from rape and robbery. He was in England, he said, to find his brother, who had disappeared. To repay him, the beautiful Countess offered to enlist her friend, Sherlock Holmes, to help in the search. Despite investigating a rash of audacious jewel-thefts, and already spending altogether too much time at the music-hall, the Great Detective felt there was more to the mysterious Mr Howard, and accepted the case. With the case leading to their involvement in a vicious blood-feud, a spectacular daylight robbery and the possibility of a serious diplomatic incident Holmes and Watson must bring the case to a close, in a thrilling climax below the brooding River Thames.