Terror By Night offers a nice change of pace in the old Sherlock Holmes series of films starring Basil Rathbone as the great detective. The action takes place completely outside the confines of London and 221B Baker Street, centering on a train ride from London to Edinburgh. Holmes has been hired to safeguard an ill-fated diamond called the Star of Rhodesia on Lady Margaret Carstairs' trip home, but he's not alone. Good old Inspector Lestrade is also onboard, posing as a fisherman on holiday. Despite the presence of Holmes, Watson, and Lestrade, though, Lady Margaret's son is murdered and the jewel stolen. The jewel must be in one of the compartments onboard the train, and Lestrade quickly takes over the questioning and searching of the passengers. Dr. Watson - God bless him - also attempts his own investigation, which bears only ignominious - and comical - results.
There are a number of real characters onboard the train, each one of them suspicious in some way or other. There's a rather impertinent young lady accompanying her mother's coffin, a most disagreeable professor, an older couple concerned about the police presence around them, Watson's old friend Major Duncan-Bleek, as well as several train employees. The fact that we the viewers are kept unaware of the culprit's identity until the end is a definite plus - as is the fact that the guilty party turns out to be a jewel thief of much renown. There's as much light comedy as there is drama until the endgame is set in motion, and the ending offers a surprise or two that rescues the film from the realm of the merely average. Terror By Night is not the best of the Rathbone Sherlock Holmes films, but it's certainly an entertaining, reasonably compelling entry in the series.