Last episode to feature David Burke as Doctor Watson.
The opening title music for this episode is changed to a more sombre and distressing version.
The end credits roll up against a black screen next to an image of Sherlock Holmes and Professor Moriarty falling into the Reichenbach Falls.
Conan Doyle's original story has been somewhat expanded - there is no theft of the Mona Lisa in the original, nor any reference to such a crime. (The Moriarty plot foiled in Paris by Sherlock Holmes in the original story is not described). However, this invention of the scriptwriter does refer to a popular urban legend - which has no basis in provable fact - to the effect that the American millionaire J.P. Morgan hired men to steal the Mona Lisa for him and replace it with an exact copy. The American millionaire in this story is un-named in the credits, but Robert Henderson, who plays him, bears some resemblance to Morgan - and is briefly addressed as "Mr. Morgan" by Moriarty (if you listen closely).
This episode is based on Sir Arthur Conan Doyle's story The Adventure of the Final Problem, which first appeared in The Strand magazine in December, 1893.
Click here to read the original story.