When Holmes and Watson set out to track down a civil contractor who leaked classified information, their lives are disrupted when they are targeted by the group of cyber-activists protecting him. Tony Award Winner Steve Kazee guest stars.
Sherlock's brother, Mycroft, arrives in New York and enlists Holmes and Watson to help solve a case involving his former fiancee. Meanwhile, Sherlock has a difficult time accepting Mycroft and Joan's relationship.
When a hedge fund manager who was also running a Ponzi scheme is murdered, Holmes and Watson must determine which of his clients is guilty. Also, Sherlock contemplates sponsoring a fellow recovering addict.
Holmes and Watson come face to face with Moriarty when their one-time adversary is brought in as a consultant on a kidnapping case. Meanwhile, Detective Bell continues his struggle on the road to recovery. Natalie Dormer Returns as Moriarty.
When a body is found in a barrel, Holmes and Watson launch an investigation into the mafia's ties to the murder. Meanwhile, Sherlock attempts to make amends with Detective Bell. Peter Gerety and Paul Sorvino guest star.
When Joan revisits one of Sherlock's cold cases, she discovers an unsolved murder is connected to a rare prehistoric fossil. Meanwhile, Sherlock finds himself in uncharted territory when his duties as a sobriety sponsor cross his personal boundaries.
Holmes' latest investigation takes him inside a professional dance company when an up-and-coming ballerina is murdered. Meanwhile, Watson embarks on a solo enquiry to find a homeless veteran when his friend alleges he was abducted.
Holmes and Watson consult on a case in which a man suspected of murdering his wife years ago receives a ransom demand for her safe return. Meanwhile, Lestrade overstays his welcome at the brownstone and seems unwilling to leave.
When a famous cancer researcher is found dead, Holmes and Watson must determine if the scientist's untimely demise was tied to his latest cutting-edge invention. Meanwhile, Bell is finally cleared to re-enter the field.
When Sherlock's brother Mycroft makes a surprise return to New York, his motivations cause discord between Sherlock and Joan. Meanwhile, a missing person case takes Sherlock and Joan inside the world of unmanned aeronautics.
With Watson kidnapped, the Holmes brothers are extorted to buy her back by acquiring something the gangsters greatly value. As the clock runs down on Watson's life, Sherlock is forced to work with his despised brother Mycroft.
Rising tension between Sherlock and Watson bring their partnership to a crossroads, but they endeavor to put their differences aside while they help Sherlock's brother, Mycroft, who faces accusations of treason and murder. Rhys Ifans returns as Mycroft Holmes.