Terror by Night is the penultimate film in the series and it's also the shortest, with a running time of just under an hour. It's one of my favourites in the series and it features air pistol–toting jewel thieves, great character acting, a fast paced plot, and best of all – well for me anyway – it's set on a train, The Flying Scotsman. Terror by Night also has some of the most enjoyable scenes and comedy moments in the series, and the villain of the piece is Moriarty's notorious lieutenant, Colonel Moran, who's aboard the train to acquire a very famous and very valuable diamond — the Star of Rhodesia.

Synopsis

The film opens with some stock footage illustrating how the famous Star of Rhodesia, the world's largest diamond, was discovered in India. With the scene set, the action starts at a coffin maker's shop in London, where Vivian Vedder is flirting with the proprietor and displaying a unique interpretation of the cockney accent. She arranges with him to have her mother's coffin put on The Flying Scotsman bound for Edinburgh.

Sherlock Holmes awaits Dr. Watson's arrival at Euston Station to board the Flying Scotsman, he's been tasked with keeping the famous Star of Rhodesia safe while its owner, Lady Margaret Carstairs, travels with it to Edinburgh. While he waits, Holmes discusses the security arrangements for the Star of Rhodesia with Lady Carstairs' son, Roland Carstairs. Watson has to run to catch the train and literally leaps aboard, along with his old army friend, Major Duncan Bleek. Inspector Lestrade is also on the train to keep an eye on proceedings, pretending to be on an [out of season] fishing trip.

The plot soon starts to thicken as Holmes and Watson sit down to supper in the buffet car and Holmes finds a warning note on his plate. As Watson and Major Bleek discuss the finer points of a good curry, and Holmes tucks into a steak and kidney pudding, Roland Carstairs is killed in his carriage and the Star of Rhodesia stolen. On inspecting the murder scene, Holmes deduces that Carstairs was probably poisoned. Holmes begins his own avenues of investigation, while Watson and Lestrade question everyone on the train. In the process, Watson encounters the irascible Professor William Kilbane before uncovering a fiendish teapot thief.

Holmes and Lestrade continue to question the passengers and the investigation turns perilous for Holmes when he goes to inspect a suspicious open door and he is nearly pushed out of the train to his death. Holmes and Watson examine the coffin brought on board by Vivian Vedder and they find a secret compartment large enough to carry another person. Upon inspection, however, the Star Of Rhodesia is nowhere to be seen.

Holmes soon realises that the thief is one of his nemeses, the notorious Colonel Sebastian Moran, aboard the train under an alias. Holmes questions Vivian Vedder again, and this time she admits she was paid to bring the coffin aboard by a man who's name she can't remember. Holmes reveals he has the real Star Of Rhodesia, and it was a fake that he put in its place that was stolen.

One of the train guards is murdered the same way Roland Carstairs was, by poison dart. Another guard is knocked unconscious by Moran's henchman Sands, who was smuggled aboard in the coffin. The colonel is revealed to be Watson's friend, Major Duncan Bleek, who orders Sands to knock out Lestrade and steal the real diamond. However, Moran double-crosses Sands, kills him with a poisoned dart fired from an air pistol and takes the Star of Rhodesia. The train makes an unscheduled stop and Inspector McDonald comes on board with some bobbies.

Holmes has taken over from the temporarily incapacitated Lestrade and he explains the situation to Inspector McDonald, who soon confronts Moran/Bleek along with Vivian Vedder. Holmes is explaining how he solved the crime when the carriage lights suddenly go out and a scuffle ensues. After Holmes manages to handcuff Bleek / Moran, the lights come back on and he's ostensibly led away, cloaked under Insps. McDonald's jacket. Holmes then reveals that McDonald actually took Lestrade away under his jacket. When Lestrade gets outside the station, he arrests 'Inspector McDonald' and his cohorts who were posing as bobbies – Holmes knew the real Inspector McDonald and spotted the imposter straight away.

Holmes and Watson sit chatting to a handcuffed Colonel Moran and in a final twist, Holmes pulls out the Star Of Rhodesia, which he had switched once again.