Sherlock agrees to take a case from a man claiming to be Moriarty, hoping it will bring him closer to finding his nemesis. Meanwhile, Gregson encourages Joan to give up the dangerous line of work she has chosen and go back to being a sober companion.

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. Meanwhile, Joan takes the advice of a friend and signs up for an online dating service.

When a financial consulting company CEO is poisoned to death, a woman from Sherlock's past who emerges as a possible suspect.

Holmes and Watson find themselves digging through the dark world of the mob to find a killer when they discover the body of a former assassin. Meanwhile, Watson helps a close friend track down a mystery man who swept her off her feet.

Sherlock’s brother, Mycroft, arrives in New York and enlists Holmes and Watson to help solve a case involving his former fiancée. Meanwhile, Sherlock has a difficult time accepting Mycroft and Joan’s relationship.

When a beautiful young woman is murdered, Holmes and Watson investigate her ties to a billionaire CEO. Meanwhile, Mycroft makes a case for Sherlock to move back to London.

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.