Thieves break into a warehouse that stores guns, steal them and kill the night watchman. An undercover agent assigned to the case happens to get into a traffic accident with the sister of the man the police suspect is head of the burglary ring, and in order to work his way into the gang, he romances the boss' sister. Complications ensue when the two fall in love.
Holmes, retired to Sussex, is drawn into a last case when his arch enemy Moriarty arranges with an American gang to kill one John Douglas, a country gentleman with a mysterious past. Holmes' methods baffle Watson and Lestrade, but his results astonish them. In a long flashback, the victim's wife tells the story of the sinister Vermissa Valley.
A respected war correspondent is found murdered, with three bullets--from three different guns--in him. Three different men are arrested, convicted and sentenced to death for the murder, but only one can be the actual killer. A criminologist sets out to find who is really guilty.
In London, a secret society led by lawyer Thaddeus Merrydew collects the assets of any of its deceased members and divides them among the remaining members. Society members start dropping like flies. Sherlock Holmes is approached by member James Murphy's widow, who is miffed at being left penniless by her husband. When Captain Pyke is shot, Holmes keys in on his mysterious Chinese widow as well as the shady Merrydew. Other members keep dying: Malcom Dearing first, then Mr. Baker. There is also an attempt on the life of young Eileen Forrester, who became a reluctant society member upon the death of her father. Holmes' uncanny observations and insights are put to the test.
The Wrecker wrecks trains on the L & R Railroad. One of his victims is Larry Baker's father. Baker wants to find the evildoer, among a host of suspects, but it will be difficult since the Wrecker can disguise himself to look like almost anyone
London, 1929. Frank Webber, a very busy Scotland Yard detective, seems to be more interested in his work than in Alice White, his girlfriend. Feeling herself ignored, Alice agrees to go out with an elegant and well-mannered artist who invites her to visit his fancy apartment.
Three sideshow performers form a conspiracy known as "The Unholy Three" - a ventriloquist, midget, and strongman working together to commit a series of robberies.