An assignment with the Diagnostics unit leads Bell to discover a body in a barrel. Joan ID's the victim as a member of a mafia family. Sherlock and Joan go to the victim's father's house, but he dies in a car explosion. Paperwork at the scene leads Sherlock to believe someone in the government tipped off a rival family and Sherlock's suspicions are validated when he and Joan visit an NSA front. Sherlock figures out that Bell's new boss, Da Silva, is dirty and Bell discovers evidence linking Da Silva to the mafia family. They take Da Silva down. Meanwhile, to win back Bell's friendship, Sherlock shares personal details about his life. Bell rejoins Major Crimes.