This episode features the first of four appearances by Charles Gray as Holmes' brother Mycroft.
The end credits for this episode begin over a view of Holmes walking away down a misty railway platform.
This episode is based on Sir Arthur Conan Doyle's story The Greek Interpreter, which first appeared in The Strand magazine in September, 1893.
Click here to read the original story.
ccomley writes -
George Costigan's performance would appear to have been heavily influenced by the great Peter Lorre.