Watson showrunner Craig Sweeny reveals there were almost plans for a different character to die in the season 1 finale. Based on the Sherlock Holmes stories, the cast of Watson is led by Morris Chestnut's titular character, who treats patients in Pittsburgh with his unorthodox methods. In a shocking move, the Watson season 1 finale killed off legendary nemesis and principal antagonist James Moriarty (Randall Park). He was ostensibly killed by Watson, via a custom genetic illness, adding to the shock factor of the scene. However, another character could actually have died instead, and was considered in an earlier draft of the episode.