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.
When a serial bomber becomes active again after being dormant for six years, Watson seeks help from Shinwell Johnson, a former patient whose life she saved when she was a surgeon. Holmes senses Watson is unhappy and questions whether she is still fulfilled by her detective career.
When the leader of a local street gang abducts Holmes to compel him to find the person responsible for a hit on his men, Holmes and Watson get caught in the middle of an international hunt to recover a centuries old, priceless artifact. Watson debates whether a personal favor Shinwell asks of her is outside her comfort zone.
Holmes learns a secret about Captain Gregson’s girlfriend when she hires him for a case she wants kept off of Gregson’s radar. Holmes and Watson join the NYPD’s search for an abducted woman.
Captain Gregson lobbies to include Holmes and Watson when his unit is selected to receive a city commendation for its exemplary work. As Holmes and Watson consult on the investigation into a financial analyst’s murder, they are drawn into the world of asteroid research.
Holmes and Watson have plenty of suspects when they investigate the murder of a man who led a secret life as a vigilante, “catfishing” sexual predators on dating sites and publicly shaming them. When Shinwell’s criminal record prevents him from finding a full-time job, Holmes disagrees with Watson’s plan to help him.
Holmes and Watson investigate a mass murder when a chef and his patrons are poisoned with snake venom. Detective Bell’s crush on a work colleague makes Holmes realize his and Fiona’s relationship is at an important crossroads.
Holmes and Watson search for two murderers after a base jumper is shot out of the sky by one killer, and has his parachute sabotaged by another. After Joan’s sister, Lin, thinks she sees Shinwell with a member of his old gang, Joan takes drastic measures to make sure he won’t be drawn back into a life of crime.
Joan worries Sherlock’s sobriety is at risk when she learns he has been lying to her about attending recovery meetings. Sherlock and Joan discover a man’s death caused by ingesting poisoned sausage is connected to a lab working on a breakthrough in the artificial meat industry.
When Shinwell comes to Holmes and Watson for help after he’s framed for a gang killing, they have three days to find the real murderer before he is arrested and sent back to jail.
When Watson is implicated in a DEA investigation into doctors writing illegal prescriptions, she and Holmes search for the person using her medical license to sell drugs.
Holmes and Watson race to find a woman who’s been held captive for years before the kidnapper takes drastic steps to avoid being caught. Watson becomes frustrated when Shinwell refuses to focus on his informant training with her and Holmes.
When Holmes and Watson investigate a clown’s murder upstate, they discover a connection between his death and the creation of a new weaponized virus. Watson helps Bell when he’s targeted by his new love interest Chantal’s ex-husband in attempt to sabotage her career at the district attorney’s office.
A man takes hostages, including Joan, and threatens to execute them unless Holmes finds the person responsible for the death of his son. As Sherlock investigates, the captor gives him 16 hours to find the perpetrator before the statute of limitations on the crime runs out.
Holmes and Watson investigate the murder of a former professional eSports video game player during a live video stream. Shinwell approaches Joan for advice when his teenage daughter asks to meet with him for the first time in years.
Holmes' former protégé, Kitty Winter, returns to New York after a three-year absence to warn him that a killer is eliminating everybody involved with a case they worked on together in London. Watson discovers that Kitty has a life-changing secret.
In the conclusion, Joan and Kitty try to prove that a string of murders, stemming from an old case Sherlock and Kitty solved in London, is connected to an international government conspiracy with the Defense Intelligence Agency at its center. Sherlock and Kitty’s relationship is strained after she shares life-changing news.
The police call in Holmes and Watson to consult on a homicide "heard" by a cutting edge gunshot detection system. Sherlock and Joan become suspicious of Shinwell when he's the target of a drive-by shooting that reveals a connection between him and an unsolved murder.
Sherlock and Joan question how well they know Shinwell when they investigate the possibility he may have gotten away with the unsolved murder of his friend, a fellow gang member. Sherlock and Joan’s latest case puts them on the hunt for a treasure map rumored to lead to a fortune in pirate’s gold hidden around New York City.
Holmes and Watson investigate the murder of a man Sherlock considered one of New York’s worst private investigators. Also, as Holmes stews over being beaten by Shinwell, he decides to take out his aggression by dismantling a local organization of private investigators.
Holmes and Watson get mixed up in murder and magic when they investigate the death of a magician killed while performing a classic stunt. Also, Watson suspects Bell is being targeted by the ex-husband of his girlfriend, Chantal, after a false allegation lands him the middle of an Internal Affairs investigation.
When Detective Bell’s girlfriend, Chantal, is assaulted and her ex-husband is killed soon after, in what Holmes and Watson discover is a staged suicide, they search for one suspect behind the linked crimes. Also, as Bell fights the urge to seek his own brand of justice for Chantal, Sherlock makes a heartbreaking realization about the detective’s past.
When a reality show contestant is murdered, Holmes and Watson zero in on another competitor as a suspect, a former war criminal who may be the most skilled killer they’ve ever pursued. Also, for the first time since he attacked Sherlock, Shinwell reaches out to Joan to ask for a favor.
Holmes and Watson investigate a murder that puts them in the crosshairs of one of New York City’s deadliest gangs. Also, Holmes’ behavior becomes increasingly erratic when he secretly interacts with a mysterious woman.
Holmes and Watson pursue an elusive criminal as a gang war erupts in New York City. While the NYPD works to contain the violence, the two investigate the murder that appears to have ignited the city-wide conflict, and discover that a familiar face is pulling the strings.