The forthcoming film Sherlock Holmes: A Game of Shadows will see the great detective face off against the evil Professor James Moriarty, but did you know that although he is often presented as Sherlock Holmes arch-nemesis, Moriarty and Holmes only ever encountered one another in a single short story by Sir Arthur Conan Doyle?
Entitled The Final Problem, the story has Holmes revealing that the professor (whom Holmes admits is his intellectual equal) sits at the centre of London’s underworld, like a spider in a vast web. Holmes considers the eventual capture of Moriarty and dismantling of his network to be the single greatest moment of his career. The two finally face off in a duel to the death atop Reichenbach Falls.
Moriarty did go on to appear in one other story, The Valley of Fear which although written after The Final Problem, actually takes place before it. However, the Professor and Holmes do not meet during the story.
Holmes does make reference to Moriarty in five other stories: The Empty House (the immediate sequel to The Final Problem), The Norwood Builder, The Missing Three-Quarter, The Illustrious Client, and His Last Bow, but they only ever encountered one another directly the one time.
With the adaption of the Holmes stories to feature film and television, many writer/director/producers have chosen to use Moriarty as the ongoing villain or a threat working in the shadows behind the main mystery, much as the early James Bond films made use of SPECTRE and its leader Ernst Stavro Blofeld as ongoing villians, even though the character and organization only appear in three and four books respectively.