Detective Sherlock Holmes, along with his sober companion, Dr. Joan Watson, uses his uncanny ability to read people and analyze crimes to assist the NYPD on some of their more difficult cases. In the season premiere, Holmes consults on a home invasion that resulted in murder.

Sherlock uses his powers of deduction to consult on the murder of a young man who is shot upon entering his apartment. Meanwhile, Watson has dinner with her ex-boyfriend, Ty Morstan.

Sherlock and Watson consult on a child abduction case involving a serial killer who is nicknamed "The Balloon Man," because he leaves a signature batch of balloons at each of his crime scenes.

Sherlock uses his trademark deductive reasoning skills to find the killer of a college professor. Meanwhile, Watson gets a call from a former lover who needs her help in disproving hit-and-run charges.

Sherlock is called in to investigate when a supposedly uncrackable bank vault called “The Leviathan” is breached. Meanwhile, Joan is pleasantly surprised when Sherlock meets her family and defends her choice to become a sober companion.

When Sherlock's ex-drug dealer, Rhys, comes around for help, Watson is concerned about Sherlock's sobriety after Rhys implies that Sherlock on drugs made a better detective.

Sherlock investigates a case involving a wealthy philanthropist who believes his incurable illness was given to him on purpose. Meanwhile, Sherlock tries to teach Joan his deductive skills by sending her to a suspicious dry cleaning establishment.

Sherlock and Joan hunt for the accomplice of a murdered blackmailer who targeted families of rape victims. Meanwhile, Sherlock resists celebrating his first year of sobriety.

Sherlock resumes his hunt for Moriarty when Sebastian Moran reveals that a man who was thought to be dead from a heart attack was actually on the list of intended victims from Moriarty.

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.

As Sherlock reels at the reappearance of his former lover, Irene Adler, a series of flashbacks unravel the tumultuous events that led to his downfall into addiction. Meanwhile, he and Joan once again find themselves in the crosshairs of the enigmatic Moriarty.

As Sherlock reels at the reappearance of his former lover, Irene Adler, a series of flashbacks unravel the tumultuous events that led to his downfall into addiction. Meanwhile, he and Joan once again find themselves in the crosshairs of the enigmatic Moriarty.

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.