Episode 1 : Step Nine
Holmes and Watson travel to London to help track down an old mentor and investigate an unsolved mystery. Meanwhile, Mycroft Holmes, Sherlock's estranged brother, reunites with Sherlock and reveals some secrets of his own. Rhys Ifans guest stars.
Episode 2 : Solve for X
When a well-respected mathematician is found dead, Holmes and Watson set out to solve a murder and the purpose of the highly guarded equation he was trying to decipher. Meanwhile, Watson is conflicted when the son of a former patient approaches her for a loan. Jeremy Jordan guest stars as Joey Castro, the son of Watson's former patient.
Episode 3 : We Are Everyone
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. Tony Award winner Steve Kazee guest stars.
Episode 4 : Poison Pen
When the CEO of a financial consulting company is poisoned to death, Holmes and Watson are called upon to track down the killer. Meanwhile, a woman from Sherlock's past emerges as a possible suspect. Laura Benanti guest stars as Anne Barker.
Episode 5 : Ancient History
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.
Episode 6 : An Unnatural Arrangement
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. Talia Balsam guest stars.
Episode 7 : The Marchioness
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. Rhys Ifans guest stars.
Episode 8 : Blood Is Thicker
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. William Sadler, Margaret Colin, and Rhys Ifans guest stars.
Episode 9 : On the Line
Holmes and Watson uncover the identity of a serial killer whose case has gone cold and find themselves butting heads with the NYPD.
Episode 10 : Tremors
When an investigation goes horribly wrong, Sherlock must testify in an official police inquiry which jeopardizes his and Watson's future with the NYPD.
Episode 11 : Internal Audit
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.
Episode 12 : The Diabolical Kind
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.
Episode 13 : All In The Family
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.
Episode 14 : Dead Clade Walking
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.
Episode 15 : Corpse de Ballet
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.
Episode 17 : Ears to You
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. Sean Pertwee guest stars as Gareth Lestrade.
Episode 18 : The Hound of the Cancer Cells
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.
Episode 19 : The Many Mouths of Aaron Colville
A serial killer known for biting his victims appears to be killing again, even though he was presumed dead.
Episode 20 : No Lack of Void
A pickpocket dies of anthrax poisoning, putting Holmes and Watson on the trail of the toxin's source in order to prevent more deaths.
Episode 22 : Paint It Black
Business becomes personal for Sherlock when he is forced to partner with his estranged brother, Mycroft, to solve a case with life-or-death consequences. Lucy Liu makes her directorial debut for television. Rhys Ifans guest stars as Mycroft Holmes.
Episode 23 : Art in the Blood
Holmes and Watson come into contact with MI-6, the British intelligence agency, when a standard murder investigation turns out to have international and political implications. Meanwhile, in the wake of a crisis, Watson reevaluates her relationships with Sherlock and his brother, Mycroft. Rhys Ifans returns as Mycroft Holmes.
Episode 24 : The Grand Experiment
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.