Sherlock Holmes is hired by Roland Carstairs to protect the Star of Rhodesia, a valuable diamond owned by Carstairs' mother, Lady Margaret. Fearing the diamond will be stolen during a train journey from London to Edinburgh, Holmes cleverly swaps the real diamond with a fake while in Lady Margaret's compartment. Despite his precautions, Roland is murdered and the imitation diamond is stolen. With the help of Dr. Watson and Inspector Lestrade, Holmes follows a trail filled with red herrings, uncovering the murderer's hiding place and linking the crime to Colonel Sebastian Moran, a known associate of the infamous Moriarty. Cast: - Basil Rathbone as Sherlock Holmes - Nigel Bruce as Dr. John H. Watson - Alan Mowbray as Major Duncan-Bleek / Sebastian Moran - Dennis Hoey as Inspector Lestrade - Renee Godfrey as Vivian Vedder - Frederick Worlock as Professor Kilbane - Mary Forbes as Lady Margaret Carstairs - Skelton Knaggs as Sands - Billy Bevan as Ticket Collector - Geoffrey Steele as The Honourable Roland Carstairs - Harry Cording as Mock the coffin maker Runtime: 60 minutes.