 The first series concluded with " The Great Game " , first broadcast on 8 August 2010 . The episode introduces the character of archenemy James Moriarty ( played by Andrew Scott ) to the series , who sets Holmes deadlines to solve a series of apparently unrelated cases . Written by Mark Gatiss and directed by McGuigan , " The Great Game " ends with a cliffhanger in which Sherlock and Moriarty reach a standoff involving a bomb attached to a vest removed moments earlier from Watson . 
