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.

When Captain Gregson’s home is invaded, Holmes and Watson work to find the masked gunman before he strikes again. Meanwhile, Gregson gives his team some insight into his private life.

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 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.

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.

When Sherlock and Joan join forces on a double homicide, Sherlock’s new apprentice threatens the investigation when she allows her jealousy of Sherlock and Joan's work rapport to override her better judgment.

When a debt collector is murdered, Holmes and Watson try to narrow down the suspect pool from thousands of consumers who owed the victim money. Meanwhile, Watson’s relationship with Andrew progresses when he asks her to meet his father for the first time.