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 Holmes faces criminal charges in the aftermath of his recent violent behavior and relapse, his powerful father arrives in New York to fix his estranged son’s legal difficulties by any means necessary. Also, with Holmes and Watson’s consultancy with the NYPD in jeopardy, Holmes concentrates on the case of a missing wife believed to have been killed by her husband to try and get back in the department’s good graces.
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.
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 look into the death of a member of Holmes’ online beekeeping community who was a researcher looking into a deadly Northeast honey bee outbreak. During the investigation, they meet Tara Parker, a brilliant entomologist, academic and the leader of New York’s beekeeping society. Also, Captain Gregson enlists Watson’s services in an off-book investigation that helps him make a life-changing decision.
Sherlock returns to New York with a new apprentice and a renewed interest in working with the NYPD after being fired by London’s MI6. However, Gregson won’t let him resume consulting for the department without permission from his former partner, Joan, the NYPD’s new go-to private investigator.
When Sherlock and Joan join forces on a double homicide, Sherlock’s new apprentice threatens the investigation when she allows her jealousy of Sherlock and Joan's work rapport to override her better judgment.
Sherlock helps a math genius from his network of 'Irregulars' experts after he stumbles upon a body while participating in a math puzzle competition. Joan attempts to extend an olive branch after she learns about Kitty’s past.
Sherlock takes on the case of a stolen artificial intelligence software program, but seeks out Joan when he'd rather disprove the computer's abilities than find the thief. Joan meets Sherlock head-on when she finds out he's met with Andrew without telling her.
Holmes and Kitty investigate the murder of a postal store owner whose death is connected to the illegal diamond trade. Meanwhile, Gregson's career is placed in jeopardy when he hits a fellow NYPD officer.
Holmes and Watson search for a thief who committed murder to steal a rare map. Meanwhile, Watson becomes concerned with Sherlock’s escalating interference into Kitty’s burgeoning personal life.
A bored Sherlock forces his investigative services onto Joan, who is trying to locate a woman who has been missing for five years, and the only clue is the smell of nutmeg at the site of her disappearance. Meanwhile, Joan’s bond with her long-distance boyfriend, Andrew, is tested when a man from her past reappears and asks for her help.
Holmes and Watson join forces with the NYPD after a police officer is murdered. Also, Sherlock searches for the creator of a “recovery blog” who is posting personal statements he has made in sobriety meetings.
When Watson joins forces with Holmes and Kitty to locate a missing nurse she used to work with, the woman’s trail leads them to another person who has recently disappeared.
While Kitty tries to find a runaway teen, Sherlock and Joan work a case in which the murder of a brilliant bioengineer looks to be at the hands of a drug cartel. Also, Joan makes a major life decision but worries it will impact Sherlock negatively, not knowing that Sherlock has big news of his own.
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.
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.
When a debt collector is murdered, Holmes and Watson try to narrow down the suspect pool from thousands of consumers who owed the victim money. Meanwhile, Watson’s relationship with Andrew progresses when he asks her to meet his father for the first time.
An unexpected event brings Watson into contact again with Elana March, the crime boss she brought to justice. Also, with Watson distracted, Holmes partners with Detective Bell to investigate a theft at a local zoo.
Holmes and Watson follow a blood trail into the world of wrongful death compensation when they investigate a series of murders in which the killer leaves envelopes of cash on the victims. Also, Holmes makes a generous gesture towards Watson as she suffers through the aftermath of a personal crisis.
When Holmes is implicated in the murder of a woman who was killed during the height of his addiction, he investigates himself to find their connection. As Holmes retraces his steps with Watson’s help, the clues make his confidence in his own character waver.
Holmes and Watson investigate a murder that initially looks like a road rage incident, but takes a new direction when they learn the victim was flash-frozen at the time of death. Also, when Watson’s mother finds out Joan’s brother is cheating on his wife, she puts Joan in the awkward position of confronting him about the affair.
When a driver for a ridesharing company is intentionally run over by a city cab, Holmes and Watson wonder if it’s a case of professional jealousy. A casual romance Holmes has with one of his longtime “Irregular” consultants becomes complicated when the woman makes a shocking request.
Holmes and Watson find themselves in the middle of a civil war being fought on the Internet when a member of Everyone, the anonymous hacker group they periodically work with, is murdered.
Holmes and Watson investigate the murder of a professional skeptic, a man who debunked paranormal, religious and scientific phenomena for a living. The case becomes urgent when his homicide reveals a potential threat to homeland security. Also, Captain Gregson’s daughter and fellow NYPD officer, Hannah, asks Watson for help with one of her cases.
When two New York City paramedics are killed during a kidnapping, Holmes and Watson join the manhunt to find the murderer and the woman he abducted. Also, Holmes learns important information about his recovery sponsor, Alfredo, that strains their relationship.
When a judge is murdered, Holmes and Watson become involved in the interstate search to find the prime suspect, an escaped convict from a privatized prison. Also, when Holmes applies his deductive reasoning to Detective Bell’s new relationship, the romance hits a rough patch.
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.
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.
Even though he despises bankers, Holmes agrees to consult on a case involving the death of a Wall Street executive who appears to have overdosed on heroin. Meanwhile, with Holmes’ encouragement, Watson tries to re-enter the dating scene.
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 tries to prove that one of the people whose body was found in the wreckage of a small plane crash was actually killed before the plane went down. Meanwhile, Watson tries to convince Sherlock to meet with his elusive father.
Sherlock assists with a double homicide that has the same M.O. as a series of murders that took place 13 years ago. Meanwhile, after being frozen out by Sherlock, Watson visits his old rehab center in order to learn more about the mysterious man in her care.
While investigating an explosion that kills two people, Sherlock discovers a crime that’s been lying dormant for years. Meanwhile, Watson encourages Sherlock to finally pick a sponsor.
Sherlock uses his trademark deductive reasoning skills to find the killer of a college professor, Watson gets a call from a former lover who needs her help.
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.
Sherlock and Joan investigate the murder of the general manager of a high-end Manhattan hotel whose body is found inside an industrial laundry machine. Meanwhile, since Joan’s time with Sherlock is almost up, he offers her an apprenticeship.
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.
While on suspension from the NYPD, Sherlock investigates a suspicious hit-and-run accident involving a conspiracy theorist. Meanwhile, Watson tries to broker peace between Sherlock and Gregson.
Sherlock pursues Martin Ennis, an unpredictable criminal, before he strikes again. During the investigation, Sherlock is forced to work alongside Kathryn Drummond, the FBI profiler who literally wrote the book on Ennis. Meanwhile, Watson faces eviction from her apartment.
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 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.
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.
Joan investigates her first solo case when a wife disappears. The missing woman left behind a tear-filled video that mentions a murder on a subway platform. While Joan searches for the vanished lady, Sherlock probes the murder.
Sherlock and Joan try to prevent the largest cash vault in the U.S. from being robbed during a deadly blizzard. Meanwhile, Holmes attempts to help a transgender woman who is recovering from her latest breakup.
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. Sherlock and Joan once again find themselves in the crosshairs of the enigmatic Moriarty.
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.
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.
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.
When a financial consulting company CEO is poisoned to death, a woman from Sherlock's past emerges as a possible suspect.
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.
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.
Sherlock’s brother, Mycroft, arrives in New York and enlists Holmes and Watson to help solve a case involving his former fiancée. Meanwhile, Sherlock has a difficult time accepting Mycroft and Joan’s relationship.
When a beautiful young woman is murdered, Holmes and Watson investigate her ties to a billionaire CEO. Mycroft makes a case for Sherlock to move back to London.
Holmes and Watson uncover the identity of a serial killer whose case has gone cold and find themselves butting heads with the NYPD.
When an investigation goes horribly wrong, Sherlock must testify in an official police inquiry which jeopardizes his and Watson’s future with the NYPD.
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.
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.
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.
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.
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.
Tensions rise when Holmes and Watson are forced to partner with Gareth Lestrade, Sherlock’s former Scotland Yard colleague, on a bombing investigation.
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.
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.
A serial killer known for biting his victims appears to be killing again, even though he was presumed dead.
A pickpocket dies of anthrax poisoning, putting Holmes and Watson on the trail of the toxin’s source in order to prevent more deaths.
When Sherlock’s brother Mycroft makes a surprise return to New York, his motivations cause discord between Sherlock and Joan. Meanwhile, a missing person case takes Sherlock and Joan inside the world of unmanned aeronautics.
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.
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.
Rising tension between Sherlock and Joan brings 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.