A convicted thief in Dartmoor prison hides the location of the stolen Bank of England printing plates inside three music boxes. When the innocent purchasers of the boxes start to be murdered, Holmes and Watson investigate.
Sherlock Holmes
Basil Rathbone
Dr. John H. Watson
Nigel Bruce
Mrs. Hilda Courtney
Patricia Morison
Colonel Cavanaugh
Frederick Worlock
Hamid
Harry Cording
Inspector Hopkins
Carl Harbord
Ebenezer Crabtree
Holmes Herbert
Julian 'Stinky' Emery
Edmund Breon
Evelyn Clifford
Patricia Cameron
Mrs. Hudson
Mary Gordon
Commissioner of Scotland Yard
Ian Wolfe
Tour Guide
Leyland Hodgson
Antique Shop Assistant (uncredited)
Marjorie Bennett
Detective at Murder Scene
William H. O'Brien
Photographer
Frank Baker
Sally Shepherd
Joe Cisto
Wallace Scott
Pub Patron (uncredited)
Jack Curtis
Convict at Dartmoor Prison (uncredited)
Cyril Delevanti
Cab Driver (uncredited)
Charlie Hall
Alfred - Auction House Bookkeeper (uncredited)
Olaf Hytten
Pub Patron (uncredited)
Frank Mills
Minister's Wife (uncredited)
Lillian Bronson
Pub Patron (uncredited)
Bobby Hale
Crabtree's Assistant at Auction (uncredited)
Alexander Pollard