The film is based on Sir Arthur Conan Doyle's 1890 novel of the same name, the second novel to feature Sherlock Holmes and Doctor Watson.

[2] Charles Edward Pogue was enlisted to pen the screenplays[2] but only The Sign of the Four and The Hound of the Baskervilles were ultimately filmed as Granada Television's Sherlock Holmes series premiered in 1984.

You see, when Sy Weintraub was planning the films, he was unaware that the copyright on the Holmes stories was about to expire in England and he had to go through a great deal of legal negotiations with the Conan Doyle estate in order to gain permission to use them.

He had a very good case, apparently; but eventually there was an out of court settlement for an extraordinary sum of money - something like two million pounds - which was enough for Weintraub to cover his costs on both The Sign of Four and The Hound of the Baskervilles, and make a profit, too.

And so he wrapped the project up.The Sign of Four was shot simultaneously with The Hound of the Baskervilles[3] but the schedule precluded having David Healy portray Watson in both films so Donald Churchill was enlisted to play the role in The Hound of the Baskervilles.