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.

• Universal Pictures
• Basil Rathbone
• Nigel Bruce
• Marjorie Riordan
• Rosalind Ivan
• Morton Lowry
• Leslie Vincent
• Martin Kosleck
• Rex Evans