Following his fall from grace in London and a stint in rehab, eccentric Sherlock escapes to Manhattan where his wealthy father forces him to live with his worst nightmare – a sober companion, Dr. Watson. A successful surgeon until she lost a patient and her license three years ago, Watson views her current job as another opportunity to help people, as well as paying a penance. Holmes resumes his work as a police consultant in New York City and Watson has no choice but to accompany her irascible new charge on his jobs. But Sherlock finds her medical background helpful, and Watson realizes she has a knack for playing investigator.
With the mischievous Sherlock Holmes now running free in New York solving crimes, it’s simple deduction that he’s going to need someone to keep him grounded, and it’s elementary that it’s a job for Watson.
As Holmes faces criminal charges in the aftermath of his recent violent behavior and relapse back into heroin, his position with the NYPD is put in jeopardy. Holmes concentrates on the case of a missing wife believed to have been killed by her husband to try to get back in the department’s good graces, while at the same time expecting a visit from his father.
When Morland offers to use his influence to have Sherlock and Joan reinstated as consultants to the NYPD, Sherlock’s mistrust of his father makes him question his motivation to help. Also, with no work offers coming in, Watson wrangles a gig with the FBI investigating a triple homicide in a top secret research lab.
When Sherlock finds himself distracted by his father’s ongoing presence in New York City, he offers to help Morland resolve a work issue in exchange for his prompt departure home. Also, Holmes and Watson’s investigation into the double murder of two men who looked alike leads them into the world of facial recognition technology.
When Holmes and Watson investigate the murder of a fertility lab technician, they discover the woman had a secret personal life that leads them to multiple suspects. Also, the tables are turned on Watson when she’s investigated by an NYPD detective.
When an archeologist is murdered, Holmes and Watson believe the man may have been killed for what he discovered during his last excavation in a local landfill. Also, Sherlock’s relationship with Alfredo, his friend and former sobriety sponsor, hits a rough patch.
Morland offers to act as one of his son’s “Irregular” consultants so that he can lend Sherlock and Joan his considerable resources to help them solve a case.
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 investigate a homicide in which the victim was murdered in a manner reminiscent of the crimes of an infamous, and already incarcerated, serial killer. Also, Sherlock and Joan tutor Detective Bell for a police sergeant’s exam that would lead to a promotion and a post at another precinct.
Holmes and Watson search for a computer hacker responsible for three murders, including the death of a Russian billionaire who was visiting New York City. Also, Joan is surprised to receive a solo dinner invitation from Sherlock’s father.
Holmes’ tentative reconciliation with his father suffers a setback when Holmes and Watson discover Morland has been keeping a secret that threatens all of their safety. Also, Holmes and Watson investigate two murders connected to a for-profit college and its illegal recruitment practices.
Holmes and Watson must search for a killer without any physical evidence to aid them after a bomb is detonated in the New York City morgue. Also, Watson is suspicious when an NYPD detective she’s in a grudge match with asks her to consult on a case.
Captain Gregson’s colleague from Narcotics asks Holmes to orchestrate the perfect heist inside the heavily armed and virtually impenetrable compound of a drug-dealing biker gang. Also, when Watson assists Fiona Helbron, who helped her on a recent case, she makes a surprising discovery about Holmes.
Sherlock and Joan search for a murderer who used poisonous mushrooms to kill a botany professor and a group of the instructor’s students. Also, when Joan is disturbed by loud noise next door, she discovers her neighbor, Trent, is renting out his home through a vacation site that caters to hard partiers.
When Holmes’ investigation into the attempt on Morland’s life pushes their strained relationship to the breaking point, the identity of Sherlock’s mother is revealed. Also, when three gang members are murdered, Holmes and Watson are amazed when an elderly woman emerges as their prime suspect.
When Watson runs into Captain Gregson and his secret girlfriend, a former NYPD officer, she inadvertently sets the couple’s breakup in motion. Also, Holmes and Watson investigate the murder of a wealthy woman who left her considerable estate solely to a beloved dog.
At the urging of Morland’s wealthy associate, Henry Baskerville, Holmes and Watson look into the death of his brother and discover that a witness saw the man chased to his death by a large, glowing animal too fantastic to be real. Sherlock considers intervening when the trauma from the bombing at the morgue negatively impacts ME Hawes’ work.
When a vigilante dressed up as a comic book hero is murdered, Holmes and Watson need to find the man's true identity and find his killer. Also, Morland makes a surprise donation to Watson’s favorite charity, in order to compel her to do him a business-related favor.
When a survivalist doctor goes missing, Holmes and Watson must determine whether he’s purposely gone off the grid or if he’s a victim of foul play. Also, Holmes exhibits odd behavior when his romantic relationship with Fiona hits a critical point.
A mysterious woman who organizes illegal, high-stakes poker games arrives on Holmes and Watson’s doorstep and tells them her life is in danger claiming to be a former associate of Mycroft, Sherlock’s brother. However, as the pair investigates, Joan becomes suspicious that their new client isn’t being truthful.
As Holmes and Watson investigate a woman’s murder, they discover her death is linked to a piece of artwork that has ties to a crime that was committed when she was in college. Also, in the wake of a shocking personal revelation, Watson attempts to forge a connection with a recent client.
When Holmes and Watson are pulled into a double-homicide investigation, they discover the victims were staging a fake murder right at the moment they were killed. Also, Watson’s inside man at Morland’s office encounters a problem that threatens to expose her spying to Holmes and his father.
Sherlock’s father, Morland, becomes Sherlock and Joan’s prime suspect in a murder investigation after one of his employees is killed under the guise of a robbery.
When Holmes and Watson discover the perpetrator behind the attempt made on Morland’s life, they find a shocking connection to themselves.
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.