After Jim Moriarty is arrested his brother is out for revenge and goes on a killing spree, forcing John and Sherlock to work with Moriarty as he is the only who can help them. Sherlock is afraid of Moriarty hurting John so they do their best to keep their new relationship a secret from Moriarty. What Sherlock and John don't know is that Moriarty is obsessed with John, he is plotting to make John his and will do anything to get him.