Holmes and Watson face their greatest challenge to date when a murder investigation threatens to destroy their partnership.

As Kitty begins to unravel due to the imminent threat to her safety, Sherlock and Joan intensify their efforts to help her. Also, the origin of Sherlock and Kitty’s relationship is revealed.

Amidst Holmes and Watson’s battle with tech billionaire Odin Reichenbach, the investigators receive word of their old enemy and Sherlock’s former love, Jamie Moriarty.

Holmes and Watson join forces with Holmes’ father, Morland, to enlist his vast criminal network to help disassemble tech billionaire Odin Reichenbach’s crime prevention system.

Tech billionaire Odin Reichenbach inadvertently provides Holmes and Watson with a lead that could give them evidence that brings him to justice.

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.

Holmes and Watson find themselves on the hunt for a serial killer after a murder rocks their inner circle. Also, Holmes’ neurological recovery regresses and his sobriety wavers as his commitment to catching the killer grows into an obsession.

Sherlock is reunited with “M.” a British criminal who appears to have followed Sherlock to New York. Meanwhile, Joan has reservations about leaving Sherlock and taking on a new client.

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.

Holmes and Watson’s lives are threatened by an influential, worldwide criminal network connected to the murder attempt on Morland Holmes. Also, Sherlock’s grievances with his father threaten their alliance to bring their mutual adversary to justice.

Holmes and Watson search for a killer choosing victims based on the predictions of a deceased man who claimed to foresee the future deaths of others, including the murder of Sherlock Holmes.

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.

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.

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.

When Watson’s stepfather writes a crime novel based on her work with Holmes without her knowledge, an underlying issue in their relationship is revealed. Also, as Holmes and Watson investigate a retired FBI agent’s murder, they discover the man’s death is connected to an unsolved case from the victim’s career.

Holmes and Watson’s new careers as consultants for Scotland Yard in London take them inside the tabloid journalism industry when a popular model is the victim of an acid attack. Also, as Watson grows increasingly homesick for New York, Captain Gregson is wracked with guilt over his unresolved rift with his former consultants.

Holmes and Watson try to work a stateside investigation from London when someone close to them is gravely wounded by an unknown perpetrator in the United States. However, Holmes’ stateside legal trouble – the result of a confession to a murder he didn’t commit – threatens to derail their efforts.

Holmes takes extreme measures to secure his return to New York when he leans on his father’s disreputable connections to aid his legal re-entry into the United States. Also, while Holmes looks for a way back to the United States, Watson helps the NYPD investigate a murder at a storage facility that caters to wealthy clients with items they want hidden from U.S. Customs.

Tech billionaire Odin Reichenbach hires Holmes and Watson to investigate a personal threat he suspects originated from within his own company; Holmes and Watson search for a motive behind three seemingly unconnected murders.

Sherlock tries to determine who has been killing weak and terminal patients at a hospital, making it look like they died of natural causes. Meanwhile, Sherlock learns more about Joan’s decision to walk away from her surgical career.

Sherlock investigates what he believes will be an open-and-shut case after Detective Bell is attacked. However, the case takes an unexpected turn when the suspected assailant is found dead. Meanwhile, Sherlock encourages Joan to learn self-defense.

Holmes and Watson uncover the identity of a serial killer whose case has gone cold and find themselves butting heads with the NYPD.

Watson begins her new job as an in-house investigator for an insurance firm. However, her attention shifts to a case that is personal for both her and Holmes when they join forces to eliminate an imminent threat to Kitty.

Holmes and Watson take on an investigation of a personal nature when Holmes’ recovery sponsor, Alfredo, suddenly disappears. As they delve into Alfredo’s life for clues, Holmes questions whether their friend has been abducted, or worse, if he suffered a relapse into addiction.

Holmes and Watson discover that the murder of a robotics engineer may be connected to his groundbreaking secret research in the area of real-life teleportation. Also, when Detective Bell is shut out of a required class he needs in order to complete his master’s degree and join the U.S. Marshal Service, he is shocked to discover the course instructor has personal reasons for denying him access.