When a woman is found dead with her throat torn out, the local villagers blame a supernatural monster. But Sherlock Holmes, who gets drawn into the case from nearby Quebec, suspects a human murderer.
Lucky is tricked into missing his own wedding to Margaret and has to make $25,000 so her father will allow him to marry her. He and business partner Pop go to New York where they run into dancing instructor Penny. She and Lucky form a successful dance partnership, but romance is blighted by his old attachment to Margaret and hers for Ricky.
Holmes and Watson board a passenger train bound from London to Edinburgh, to guard the Star of Rhodesia, an enormous diamond worth a fortune belonging to an elderly woman of wealth; but within the first hour of the trip, the woman's son is murdered and the diamond stolen and any of the passengers in their car could be the killer thief.
