Terror by Night (1946) hints at a few of Sir Arthur Conan Doyle's original stories. The action takes place on a speeding steam train racing from London to Edinburgh. Lady Margaret Carstairs possess a 423 karat diamond, known as the 'Star of Rhodesia' and her son employs Holmes to protect the priceless jewel until it reaches its home in Scotland. Lady Margaret's son is found murdered and the 'Star of Rhodesia' has been whisked away. Eccentric and suspicious passengers line the Scotland Express as Sherlock Holmes, Dr. Watson and Inspector Lestrade (Dennis Hoey) investigate. Along for the ride is an old friend of Watson's, Major Duncan-Bleek (Alan Mowbray), who may or may not be as disinterested a party as he appears.