Heston played Holmes in the Los Angeles theatrical version of the play in preparation for the role although the stage version was mounted in December 1980 and January 1981, ten years before the movie. Jeremy Brett, who later became one of the most acclaimed Holmes, played Watson.
Kiran Shah reprises his role as 'Tonga' from his initial rendition of the character in the Granada Television production Il Segno dei Quattro (1987).
Charlton Heston had been briefly considered by Walter Mirisch for " The Private Life of Sherlock Holmes " but director Billy Wilder wasn't keen on the idea. Richard Attenborough would have been Doctor Watson.
Charlton Heston (Sherlock Holmes), Richard Johnson (Dr Watson), Clive Wood (Jonathan Small) and James Coyle (Birdy Johnson) had all previously appeared in 1990's Treasure Island. Like this film, that one was also directed by Fraser C Heston
Based on Sir Arthur Conan Doyle's The Sign of the Four with substantial alterations to many plot points.