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.
On the eve of the Chinese New Year, three strangers, Crystal Shackleford, married to a wealthy philanderer; Jerome Artbutny, an outwardly respectable judge; and Johnny West, a seedy sneak thief, make a pact before a small statue of the Chinese goddess of Destiny. The threesome agree to purchase a sweepstakes ticket and share whatever winnings might accrue.
Cashier and part-time starving artist Christopher Cross is absolutely smitten with the beautiful Kitty March. Kitty plays along, but she's really only interested in Johnny, a two-bit crook. When Kitty and Johnny find out that art dealers are interested in Chris's work, they con him into letting Kitty take credit for the paintings. Cross allows it because he is in love with Kitty, but his love will only let her get away with so much.
Ten strangers are summoned to a remote island and while they are waiting for the mysterious host to appear, a recording levels serious accusations at each of the guests. Soon they start being murdered, one by one. As the survivors try to keep their wits, they reach a disturbing conclusion: one of them must be the killer.
Sherlock Holmes investigates when young women around London turn up murdered, each with a finger severed. Scotland Yard suspects a madman, but Holmes believes the killings to be part of a diabolical plot.
The Good Comrades are a collection of varied gentlemen who crave one thing - solitude. They reside at Drearcliff House, ancestral home of their eldest member. All seems serene and convivial until one by one the members begin to perish in the most grisly of manners. Foul play is suspected by the Good Comrades' insurance agent, who turns to Sherlock Holmes and Dr. John Watson for guidance.
Mortimer Brewster, a newspaper drama critic, playwright, and author known for his diatribes against marriage, suddenly falls in love and gets married; but when he makes a quick trip home to tell his two maiden aunts, he finds out his aunts' hobby - killing lonely old men and burying them in the cellar!
The famous Borgia Pearl, a valuable gem with a history of bringing murder and misfortune to its owner since the days of the Borgias, is brought to London, thanks in part to Sherlock Holmes. But before long the jewel is stolen, due to an error on Holmes' part, and shortly thereafter, a series of horrible murders begin, the murderer leaving his victims with their spines snapped and surrounded by a mass of smashed china.
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.