Sherlock Holmes is approached by Inspector Hopkins to help solve the murder of Willoughby Smith. He was the assistant of Professor Coran, an invalided expert on ancient writings and religions, and was found by the maid. His dying words to her were "Professor, it is she". As luck would have it, Dr Watson is not available and Sherlock's brother Mycroft is visiting so lends his intellectual might to the investigation.
Another intriguing mystery in the Sherlock Holmes canon and evidence that the great quality of the previous episode was not a once-off (the series suffered somewhat in the latter episodes of The Case-Book of Sherlock Holmes and the first episode of The Memoirs of Sherlock Holmes wasn't that great either).
Good plot and Jeremy Brett is in good form as Sherlock Holmes. Making this episode even better is the presence of Mycroft Holmes (expertly played by Charles Gray). Sherlock once said that Mycroft was the only person who was his intellectual superior and the cerebral rivalry shows. There's even an element of jealousy in some of Sherlock's actions. It certainly makes for a refreshing different dynamic to the usual Sherlock-Dr Watson one.