After the King of Ruthenia has been assassinated, Holmes and Watson are engaged to escort his son to Europe via Algiers, aboard a transatlantic ocean liner which also carries a number of suspicious persons, any of whom may be involved in a plot to also assassinate him.
Sherlock Holmes
Doctor Watson
Sheila Woodbury
Agatha Dunham
Steward
Nikolas Watson
Mirko
Gregor
Jodri
Kingston
Gubek
Prime Minister
Matthias Cherney (uncredited)
Aide (uncredited)
Stimson (uncredited)
Steward (uncredited)