 Andrew Scott made his first appearance as Jim Moriarty in " The Great Game " . Moffat said , " We knew what we wanted to do with Moriarty from the very beginning . Moriarty is usually a rather dull , rather posh villain so we thought someone who was genuinely properly frightening . Someone who 's an absolute psycho . " Moffat and Gatiss were originally not going to put a confrontation between Moriarty and Holmes into these three episodes , but realised that they " just had to do a confrontation scene . We had to do a version of the scene in ' The Final Problem ' in which the two archenemies meet each other . " 
