|"Step Nine": After capturing an assassin of three U.S. Attorneys, a call on Holmes' phone results in him asking Watson to accompany him to London to help Gareth Lestrade, his old colleague. As they are packing, Holmes tells Watson his history with Lestrade. He calls him utterly adequate as a detective, but as credit for successes went to Lestrade, he began to crave the glory. At Scotland Yard, they are greeted by DCI Hopkins, Lestrade's superior. Describing the Mary Pendry case, in which Lestrade refused to let go of his suspicions and due to his extreme actions was suspended, Hopkins wants Holmes to find Lestrade. A cab delivers Holmes and Watson to 221B Baker St., Holmes's former residence in London. To his horror, he finds it has been totally remodelled and discovers that his brother Mycroft is living there. Sherlock finds Lestrade in a pub by tracking down various stashes of money that Lestrade knew about. Feeling guilty that he is responsible for Lestrade's addiction to fame, Sherlock agrees to look into the Pendry case. Sherlock finds that Mary's husband Lawrence did kill her using a plastic gun and is able to find evidence when Lawrence kills his handyman with the same weapon. Sherlock tells Lestrade that in order to break his addiction to fame, he is not to take credit for the arrest and if he does, Sherlock will discredit his involvement. The next morning, Sherlock and Watson see Lestrade on TV claiming the credit for Pendry's arrest. Mycroft texts Sherlock to meet him at a storage centre. He confesses that he didn't give away Sherlock's possessions but stored them at the centre. He says he learned from Watson that he must have Sherlock's attention when telling him something important and then blows up Sherlock's possessions using books on bomb building that were Sherlock's. Mycroft says he forgives Sherlock for everything and that things are different between them now.
"Solve for X": Bell and Holmes view the body of Felix Soto, a math tutor, on his living room floor. They both notice that one of Soto's rooms is completely empty. Holmes smells the walls and asks a confused Bell to find a black light. Holmes finds a stand-up lamp with one and once the blinds are drawn, he turns the light on to reveal math equations written on the walls. Harlan Emple explains to Holmes and Watson that Soto was trying to solve P vs. NP. He indicates that another P vs NP expert, Tanya Barrett, may know who Soto's partner is. Questioning Barrett, Holmes finds the partner is Cyril Nauer who is found dead by Detective Bell. At the Morgue, Holmes recounts that Nauer was killed an hour after Soto and, by the same killer. Barrett becomes a suspect but when questioned, provides an alibi which is confirmed by time-stamped video. Confronting Barrett in her classroom, Holmes shows that she killed Soto and Nauer as they were close to solving P vs NP and she'd altered the security footage digital time stamp.
"We Are Everyone": At The Brownstone, Holmes and Watson meet a new client, Mr. Mueller. Mueller says he represents a group of citizens concerned about Ezra Kleinfelter's safety, given that he has more secret documents he could leak. Mueller would like them to find and deliver Kleinfelter to him, so he can be taken to a friendly embassy. Holmes agrees to take the case and Mueller leaves. Having pick-pocketed a security guard's phone, who is connected to Ezra, Holmes discovers that he is a member of a cyber-activist collective "Everyone" and finds a message board, "Jamaica Quay." After Holmes wakes Watson, he reports that while debating on the board, he's deduced that a woman, Vanessa Hiskie, is hiding Kleinfelter. Watson picks the lock at Hiskie's apartment and they find her inside, dead. Having traced the security guard's phone to the Brownstone, Everyone subjects Holmes and Watson to a "life ruin". After discovering Ezra is leaving for Venezuela on a billionaire's jet, he arrested by Bell and Captain Gregson but is set free after threatening to reveal the identities of several deep cover federal agents. As Kleinfelter turns to board the plane, Watson grabs his wrist and warns him they will prove he killed Vanessa Hiskie. Watching the jet take-off, Watson produces Kleinfelter's wrist watch which she lifted from him. Impressed, Holmes asks Gregson to see if the DNA on the watch matches that found under Hiskie's fingernails. After Kleinfelter's arrest, Holmes sits by the fireplace and reads a letter from Jamie Moriarty.
"Poison Pen": Holmes and Watson are called to the home of Titus Delancey, CEO of a large financial firm, who was found dead in a bondage suit, by Mistress Felicia. Holmes discovers Titus was poisoned by nitroglycerin. Later, Holmes and Watson meet Titus' wife Peri and their nanny, Anne Barker. Holmes takes Watson outside and says that he knows her. She was the prime suspect in the poisoning death of her father, but was acquitted and her name was Abigail Spencer. In "the box" at the 11th Precinct, Gregson questions Anne who admits she was Abigail Spencer. She has no alibi but denies killing Titus. She changed her name and appearance to escape the media attention from her father's death, is angry that it will happen again and asks how they discovered her identity. Holmes says it was from her voice. Anne is released and Holmes believes that she is being framed. Watson deduces that Holmes didn't recognize Anne from her voice, but from a tattoo on her wrist. Impressed, Holmes relates that the poisoning of Anne's father catalyzed his interest in detective work. Holmes was able to deduce that she did kill her father, an abusive man, but only after the trial was over and she was acquitted. Despite this, he still believes that the framer must have discovered her past. Holmes visits Anne and reveals he is Sean Holmes. Beseiged by the media and fired as a nanny, she's still grateful to have Holmes to talk to. Bell and Watson find a tablet containing a video of Titus and Anne arguing. Later, Holmes shows Anne the video. Professing she didn't kill him, Holmes provides details from their correspondence that proves she did kill her father. Angry, Anne tells him to leave. After it's discovered Titus was abusing his son Grahame and circumstantial evidence is found that Grahame poisoned him, Anne falsely confesses to poisoning Titus. Holmes appeals to Anne but she says she's a murderer and blames herself for not noticing Graham's abuse. She views her confession as justice for what she did to her father. Holmes speaks with Graham by the river. Holmes tells him that they both know who killed Titus and that he'll be watched. He then asks Graham if he's getting help for being victimized. Graham doesn't see the point of talking about it, so Holmes provides some advice based on his past abuse and offers his services to Graham if he ever needs to talk.
"Ancient History": Watson tells Holmes about her friend Jennifer's request to find a man named Tony, who she had a one-night stand with. Pointing out that they are not busy, Holmes decides to find a case and takes Watson to the Morgue. Introducing her to Dr. Eugene Hawes, Holmes and Hawes play chess. Winning the game, Hawes gives Holmes access to the morgue's corpses. Hours later, Holmes comes upon the man who died in the motorcycle crash, Leo Banin. Holmes deduces that before Leo died, he killed someone. Watson visits the bar Jennifer met Tony at and discovers she met him on day of the Brazilian Parade. Holmes finds Watson about to watch a news tape showing the Brazilian Parade day at the bar. Unable to dissuade her, he admits that he is Tony. Shocked, she follows him to the kitchen where he explains that when she first started as his sober companion, he would follow her when she left for errands. Hoping to learn more about her, he saw her with Jennifer and passed himself off as Tony. He claims Jennifer seduced him and that once he found Watson's intentions as his sober companion were honorable, he stopped surveilling her. Holmes finds that Banin was killed by his wife, Lara, after he threatened to divorce her upon discovering she make porno movies when living in Poland. Watson meets Jennifer to let her know that Tony was Holmes but she already knows. Holmes explained everything to her and so impressed, she slept with him again. However, Jennifer is totally over Holmes. At the Brownstone as Holmes practices with Bob, Watson unsuccessfully tries to scare Holmes that he's impregnated Jennifer.
"An Unnatural Arrangement": In the holding cells at the 11th Precinct, Holmes has Watson deduce what caused the prisoners to be jailed by examining them. After Captain Gregson's wife Cheryl is threatened during a home invasion, Holmes and Watson discover the attacker entered the wrong house. This leads them to pursue various members of a US military detail who were guarding an archaeological dig in Afghanistan led by Beth Roney. Roney stole various artifacts and with her ex-husband Cameron's help, tried to sell them. Holmes and Watson provide evidence her ex was behind the Gregson's home invasion and several others in which Cameron killed members of the military detail. Holmes gives Watson a box with files on cases he hasn't been able to solve.
"The Marchioness": Mycroft asks for help with an acquaintance of his and Sherlock's. At Diogenes, Sherlock is not happy to see the acquaintance and introduces Watson to Nigella Mason, Mycroft's former fiancée. Mason explains that after Mycroft, she married a Marquess. Not fulfilling his conjugal duties, she had an affair with Dalton, who was the stable master. The affair caused her divorce but she retained her title and a champion race horse, Silver Blaze. Dalton was killed by an intruder at the stables who intended to kill the horse and she'd like them to find Dalton's killer. Deducing that Mycroft and Watson slept together when they were in London, Sherlock is protective of Watson. Sherlock captures Dalton's killer, an assassin nicknamed "El Mecánico" and finds that Nigella's troubles were her own doing after she fraudulently passed off another horse as Silver Blaze for studding a drug king's mare. Mycroft's terms for not informing the police of her fraud is her exiting the stud business and repaying those she's defrauded.
"Blood Is Thicker": Sherlock and Watson solve a case involving the murder of tech billionaire Ian Gale and his estranged daughter Haley Taylor. Both were killed by Ian's doctor wife, Natalie, for his estate. Mycroft unsuccessfully tries to lure Sherlock to return to live in London after Sherlock discusses the possibility with Watson.
"On the Line": Holmes and Watson thwart serial killer Lucas Bundsch and frees several women being held captive while dealing with a disgruntled detective, Gerry Coventry. Holmes punches Bundsch and breaks his finger. Holmes discusses Watson's rebuking of his lack of politeness with others. Although he understands the social benefits, he indicates he is not a nice man, never will be and that being acerbic helps his work. Watson points out that he is often nice to her and that he has changed since they first met, but Holmes demands that she accept that there will always be fallout from his behaviour.
"Tremors": Holmes and Watson are subjected to an administrative hearing pertaining to a case in which Detective Bell is shot. Prosecutor Cassandra Walker accuses them of breaking the law in the course of investigations. As they recount the events in solving the murder of Silas Cole, Holmes' arrogance brings retribution from a suspect, James Dylan. As Dylan tries to shoot Holmes, Bell intervenes and is hit. Bell is partly responsible for the decision to allow Holmes and Watson to continue to work with the NYPD. Holmes offers to pay for Bell to receive treatment for his arm from the foremost experts in the world which Bell declines. Bell tells Holmes to not visit him in hospital anymore and leaves.
"Internal Audit": At Alfredo's, is having a difficult time breaking into one of Alfredo's test cars. Feeling guilt for being responsible for Bell's shooting, Alfredo suggests going to a support group meeting which Holmes turns down. Investigating the murder of a corrupt hedge fund manager, Gerald Hauser, Holmes is frustrated when Watson won't let him use evidence that would reveal one of her past client's addiction. At Alfredo's, Holmes meet Randy, a recovering addict. Alfredo proposes that Holmes become Randy's sponsor. Alfredo points out that Holmes should give back to the program and it would help with the guilt he feels about Bell. Taken aback, Holmes explains that his work won't allow him to be a good sponsor. Later, Alfredo find Holmes inside his home late at night, having defeated the car's security system. Reflecting on Alfredo's request, Alfredo reminds Holmes that becoming a sponsor isn't about him. Holmes and Watson prove that Hauser was killed by Jacob Weiss, a charity CEO. Weiss and Hauser were partners in the scam but when Hauser's pyramid scheme was discovered, he told Weiss that he'd revealed the embezzlement. At the Brownstone, Holmes dictates his terms to be Randy's sponsor to him, which he accepts.
"The Diabolical Kind": When a seven-year-old girl named Kayden Fuller is kidnapped and her father shot, Holmes and Watson hear the ransom demand. Holmes quickly recognizes the voice as that of the man who previously pretended to be Moriarty, who Moriarty herself described as one of her subordinates. Assuming Moriarty gave the order for the kidnapping, Holmes and Watson visit her at a prison black site. She's made a large painting of Watson's face in perfect detail. Moriarty denies being involved in the kidnapping, but offers to give information in exchange for prison favors. Holmes refuses, but shortly afterwards discovers she has been recruited as a consulting agent by her FBI handler, Ramses Mattoo, who bring her to work with the NYPD. Moriarty provides information on the kidnappers and is accompanied to the kidnapping scene by Watson. Moriarty admits she finds Watson more intelligent and interesting than at first, and that part of the reason that she and Holmes write to one another is because they are the only ones who can understand and relate to the other. When the kidnappers ambush and kill two policemen, Holmes believes Moriarty is somehow responsible. Devon Gaspar, one of the kidnappers and a former Moriarty lieutenant calls and puts a frightened Kayden on the phone. Watson notices that Moriarty is angry when listening to the call. Moriarty is returned to her prison cell. Holmes discovers code in the sketches Moriarty made of the kidnappers but is surprised to find that Moriarty isn't behind the kidnapping she's a victim as Kayden is her daughter. Moriarty escapes her prison using glass shards of her paint jars to neutralize her stun bracelets (cutting her wrists badly) and strangles Mattoo unconscious. She tracks Gasper and the kidnappers down in an old building she owns and kills them all. She calls the police and demands that Holmes be the only one sent into for her. She tells Holmes that Kayden has been re-situated and she placed her for adoption knowing that knowledge of Kayden's existence would make her vulnerable. Moriarty believes she will soon be free and thanks Holmes for his letters. She begins to pass out from blood loss so Holmes carries her outside for treatment where Watson believes she will recover.
"All in the Family": After Bell departs the 11th for Demographics, Holmes and Watson deal with a number of incompetent detectives, including Detective Nash. At a recycling plant, Bell finds a headless, handless body in a green barrel and calls for Gregson. Bell is icy towards Holmes so Watson excuses themselves. Holmes notes the barrel's original color was blue and from a scar on the man's leg, Watson knows who the man is. In Gregson's office, he's identified as former mobster Bobby Pardillo. At Demographics, Holmes offers his and Watson's services to Commissioner Frank Da Silva. Seeing Holmes, Bell is irked to learn Holmes will be working there when Holmes knows Bell doesn't want to see him. Holmes belittles Bell's new role as an analyst and leaves. At the home of a suspect, Dante Scalice, Holmes and Watson witness him die when his car explodes. Finding printouts at Scalice's which show Bobby's movements, Holmes recognizes them as from the NSA. Holmes and Watson confront Dean McNally who denies being part of the NSA. Later in private, McNally indicates to Holmes that Da Silva asked for the printouts. Finding evidence that Da Silva is corrupt and worked for the mafia, Holmes and Watson have a difficult time convincing Bell. After Bell finds further evidence that Da Silva is dirty, Bell and Holmes set a trap in which Da Silva is caught planning to murder a mob boss. Bell returns to the Major Cases unit and makes up with Holmes.
"Dead Clade Walking": At The Brownstone, Holmes is surprised to find a guest in the library, Gay. Watson explains that while examining Holmes' box of unsolved cases, she found the murder of Doug Newberg, in which a picture of his backyard had an unusual rock. Holmes meets his sponsee, Randy, who is undergoing a crisis that requires his help. At a coffee shop, Randy tells Holmes that an ex who is a drug addict, Eve, has moved to NYC and wants to live with him while she gets sober. Without permission, Watson and Gay enter Newberg's backyard and find the rock still there. Gay says the rock is from the dinosaur era and likely contains an archaeological specimen. Holmes meets Watson at the Morgue where a technician performs a CT scan on the rock. A complete skeleton of a small dinosaur is discovered inside it. At the Triboro Museum of Natural History, they meet with Dr. Jerome Thomas by a Dimetrodon skeleton which he indicates is the only complete one in the world. After the fossil is stolen from the precinct, Holmes meets with C. who informs him that a man known only as the "Magpie" buys rare, expensive items and that if Holmes posts such as item on a website, the Magpie will reach out to him. Meeting Randy at a coffee shop, Holmes is exasperated to hear he's still involved with Eve and bluntly tells him to end it. Randy leaves the shop without Holmes knowing. On the way to the "Magpie's" home, Holmes tells Watson that Randy isn't answering his phone. Finding the door open, they enter and discover a dead man and the nanotyrannus rock smashed on the floor. At the Brownstone, Holmes wakes Watson and believes he's found the motive for smashing the fossil, a theory called "Dead Clade Walking" (DCW). At the museum, Holmes and Watson confront Dr. Jerome Thomas and accuse him of destroying the fossil and committing the murders as the fossil's existence would discredit Thomas. He's served a warrant for his DNA to match that on a murder weapon. Randy arrives and glumly tells Holmes that he got high with Eve the previous evening. He's cut Eve out of his life and understands if Holmes doesn't want to be his sponsor anymore. Holmes asks if he'd like to go to a support group meeting.
"Corpse de Ballet": At the scene of a bisected ballerina, Nell Solange, Gregson leads Holmes and Watson through the crime scene and reports that the killer took the hard drive containing the security videos. A box cutter belonging to ballerina Iris Lanzer is the murder weapon. Questioning Lanzer, Holmes is uncharacteristically polite and deferential and, he offers explanations for many of his colleagues questions. Lanzer's alibi doesn't check out and she's arrested after threatening to leave the country. After her attorney Nolan Sharp frees her, the next morning in the kitchen at the Brownstone, Watson is shocked to see Lanzer emerge from Holmes' bedroom. Confronting Holmes, he explains that Lanzer initiated the encounter and he accepted to learn more about her. Lanzer gives Holmes access to her files and at Sharp's office, Holmes starts looking over the files, he remarks on Sharp's automatic door closer. At the precinct, Bell has Holmes and Watson listen to a recording that a reporter received anonymously. Lanzer is heard leaving an angry message for Nell and it's apparent they were having an affair. At Sharp's office, they question Lanzer who admits the affair was a ploy to distract Nell from accepting the prima role. Nell ran into another dancer who Lanzer had employed the same tactics on but, Lanzer had begun to care for Nell. They made up and Nell deleted the message leading Sharp to ask how it was leaked. Holmes listens to the separated audio file on which he can hear a distinctive whirring sound he's heard before. Holmes is able to prove that the whirring sound is from Sharp's automatic door opener and he's arrested after the stolen hard drive is found in his office.
"The One Percent Solution": At The Brownstone, Watson arrives and finds Holmes has broken up a cock fighting ring. He's feeding two roosters, Romulus and Remus and intends to experiment if they can be trained to stop fighting. Gregson calls them to the scene of the explosion which killed several people from the Dept. of Labor (DoL) and a bank whose CEO is Richard Balsille. Gregson informs them that Balsille has a "security czar" they'll have to work with which, to Holmes' revulsion, turns out to be Gareth Lestrade. Holmes discovers Lestrade is arranging sexual partners for his employer, CEO Richard Balsille, and catches the bomber, MoL staffer Michelle Forrester. Fired from his job, Lestrade asks if he can stay at the Brownstone while Holmes' experiment with the roosters is a success.
"Ears to You": His confidence shattered, Lestrade is mugged and has difficulty picking a new job, despite several offers. Encouraged by Watson to solve the case of his mugging, Watson and Holmes deal with a case involving Gordon Cushing, whose wife Sarah disappeared years before. Receiving a package containing Sarah's ears, a ransom demand goes wrong and Holmes and Watson are baffled to find Sarah alive, with her ears intact. They discover her new husband, a plastic surgeon, grew ears on her back which were removed and used in the ransom demand. After finding his mugger, Lestrade believes that Holmes doctored the case to boost his confidence and seeing through Holmes' "ruse" has done the trick and he's accepted one of his job offers. He threatens to stay unless Holmes admits to the charade. Holmes shakes his hand, congratulates Lestrade and heads to the kitchen. Confused, Watson follows and asks Holmes why he didn't let her in on his plan. Holmes honestly says he's never heard of the mugger nor seen the mugging file but wanted Lestrade to move on.
"The Hound of the Cancer Cells": After Barry Granger is murdered at a laboratory, the head of the lab, Hank Prince, shows Holmes and Watson what Granger was working on, a device called "The Hound" that could detect lung cancer from breath. Without Granger and combined with an anonymous tipster who refuted the device's test results, Prince is ruined. Later, they show Prince who was behind the fake allegation and that Granger's work has been cleared. Believing that he and Granger may be the victims of corporate sabotage, Prince provides them with a list of rivals to "The Hound." Prince's wife, who he was divorcing, is then found dead. They discover that Prince discredited the Hound and killed Granger, which would temporarily lower his company's value, so that his wife wouldn't receive as much in the settlement. Once Holmes and Watson cleared the allegation against "The Hound", Prince killed his wife so she wouldn't share in its value. After much reflection, Holmes meets Bell at a party celebrating Bell's return to active duty.
"The Many Mouths of Aaron Colville": Watson learns of a "vampire killer" who bites his victims from Detective Loughlin and remembers from her time as a surgeon, Aaron Colville, a serial killer who also bit. After taking a plea deal, Colville died in 2005 during a surgery Watson was a part of. She visits Dr. Jonathan Fleming, who refuses to tell her what Colville whispered to him before he died. With the help of Everyone, Holmes gets dental records and match them to vampire killer's bite. They find that Colville's teeth were the model for dentures issued at Newgate prison. After finding a good suspect, prison dental assistant Stan Kovic, he's cleared of the murders. Watson confronts Fleming again who admits that Colville whispered that he'd killed two women. Watson tells Holmes about Fleming's confession which leads him to believe the killer knew about the dentures and wanted to cast doubt Aaron was the killer. Holmes and Watson discover Aaron's mother Ruth is the killer and find a copy of Aaron's dentures at her house.
"No Lack of Void": After discovering a man died on anthrax poisoning, Holmes reviews videos and tells Watson that Alistair died the week before of a heart attack. Gregson and Bell brief a task force that fingerprints of their prime suspect, Eugene MacIntosh. Holmes visits Alistair's partner, Ian, and discovers that Alistair was in good spirits and very healthy just before his death. He asks about Alistair's son Jeremy with whom Alistair had an acrimonious past. As Holmes stakes out a location the anthrax could be at, he notices a large delivery truck and has a conversation with an imagined Alistair which irks him. After seeing a case loaded into the truck, he breaks in and discovers the case is filled with jars of white powder and, there are letters to congressmen. Two men surprise him and in the struggle, he subdues them, but they are all covered with the powder. Later at a hospital, Watson meets Holmes who is miffed he's being tested as the powder was baby powder. Watson is angry Holmes took such a big risk when a police team was minutes away from the truck. She blames his reckless behaviour on what happened to Alistair. Watson confronts Holmes that he lied to her about Alistair who died of a heroin overdose. After an outburst from Holmes, she presses why he lied. Initially, Holmes says it was to protect Alistair's privacy but he eventually admits that Alistair helped him when he was high, something most recovering addicts wouldn't do. Given Alistair's strength, Holmes wants to find the cause of his relapse, hoping that its discovery will help him maintain his own sobriety. At Alistair's grave, Holmes imagines Alistair there apologizing for how he died. Holmes has made peace that Alistair's choices don't have to be his and, that he will miss him.
"The Man With the Twisted Lip": Mycroft returns to NYC and asks Watson out to eat at Diogenes while Sherlock and Watson search for a missing woman, Paige Dahl. At Diogenes, Mycroft proposes dating Watson and while she's interested, she's worried it would makes things with Sherlock difficult. At a park, Watson finds Paige dead in the woods while Sherlock finds a dead man, Zach Piller, against a rock. Sherlock is puzzled by shotgun blasts on the rocks around Piller and, the appearance of a mosquito, though it's winter. At Piller's former workplace, Sherlock and Watson find Piller worked for a company that makes drones. At Diogenes, Sherlock tries to stop Mycroft from dating Watson and takes a picture of a man he noticed there before. As Sherlock shows her the photo of the man, de Soto, who is a lieutenant in a French crime organization, Le Milieu, Watson expresses her anger at him interfering in her relationship with Mycroft. Believing that Mycroft is involved with Le Milieu, Sherlock then bolts out of his chair, grabs a glass and captures something on a table. Hearing clinking, he explains to Watson that he's captured a tiny surveillance drone. He now knows why there was a strange shotgun pattern around Piller's body, he and Paige were killed by drones. At Diogenes, Watson expresses her interest in dating Mycroft but indicates that she'll have to move out of the Brownstone first. She also sees a man, Marchef, who was sitting at the same table when she met Mycroft earlier and she takes his picture. At the precinct, she now agrees that Le Milieu is using Diogenes as a base and shows Sherlock her picture of Marchef who is linked to a massacre. Watson break into the office of an executive of the company Piller worked for while Sherlock meets the executive. They are able to prove that the executive ordered Piller to carry out a drone strike in Afghanistan which killed CIA operatives, then covered it up and had Piller killed. Watson heads to Diogenes where she's kidnapped by Marchef.
"Paint It Black": Hearing that Watson is kidnapped due to Mycroft's dealings with Le Milieu, Sherlock is furious with him. Mycroft explains that Pierce Norman, VP of Swiss Bank Credit Versoix, took details of thousands of their client's private banking accounts. Le Milieu wants the list. At Credit Versoix, they are shown into Norman's office by head of security, Kurt Yoder. Sherlock demands Yoder retrieve Norman's laptop and, finds a hiding place which contains a game pad. After looking at the pad, he smashes it in apparent frustration as it is useless in their investigation. At the Brownstone, Sherlock plays the video game he saw on Norman's game pad with his userid. Norman never played the game but used its chat function with one other gamer. Sherlock sends a chat to the user and waits for a response. They proceed to Westchester and question Norman's lover, Deron. A few hours after leaving Deron's, Sherlock finds a wooded river and a summer house with Norman's car outside. They proceed to the backyard where Sherlock finds a shallow grave containing Norman. Norman's body is brought into the kitchen. From a fly pupa on Norman's body, Sherlock shows that he died before the client list was stolen. Norman has been murdered and framed by someone with access to his computer. Yoder is lured to the Brownstone with news from Sherlock that they don't think Norman stole the list. Sherlock tases him into unconsciousness and after torturing him, Yoder provides the list's location. After retrieving the list, Mycroft tases Sherlock into unconsciousness.
"Art in the Blood": At the Brownstone, finding guards and Watson being attended to by a doctor, a furious Sherlock turns on Mycroft and believes Mycroft is being arrested by British Intelligence only to be told that he works for them. Meeting Mycroft's handler Tim Sherrington, he debriefs Sherlock on the rescue of Mycroft and Watson from Le Milieu and that they needn't be worried about repercussions. To Mycroft's surprise, Sherrington asks Sherlock to work on a case of an ex-MI6 analyst, Arthur West, who has been murdered. Over Mycroft's objections, Sherlock agrees to look into West. Returning to the Brownstone, Sherlock discovers that Watson wants to work so he fills her in on West's case. At the Morgue, they discover that Arthur's arms are missing. Arthur's wife, Marion, eventually reveals she tattooed numbers on Arthur's arms in infrared ink and gives them a picture of the tattoos, which are all numbers. She doesn't know what the numbers mean and that Arthur was convinced there is a mole in MI6. He did say the mole was selling secrets to a bookstore owner, Julian Afkhami. Sherlock deduces that the data represents dates and times, but to what, he doesn't know. Watson tells Sherlock that she's moving out of the Brownstone which he thinks is a knee-jerk reaction to her kidnapping. Explaining that she's planned it for a while and that she needs a life outside of detective work, he's stunned into silence and then leaves. The next morning, Sherlock meets Sherrington on a park bench, shows him the picture of the tattoos and tells him about the mole. Sherrington offers him a permanent job at MI6 but Sherlock refuses and says he's done investigating West. Gregson tells Sherlock that the gun that killed West was found with a very distinctive set of fingerprints on it that haven't been identified yet. Looking at the prints, Sherlock excuses himself suddenly and leaves. In bed at Mycroft's, Watson tells him that she's moving out of the Brownstone and that Sherlock didn't take the news well. Sherlock calls Sherrington and says he knows who the mole is. Breaking into Mycroft's, Sherlock catches them in bed and tells Mycroft that he's being framed for murder and treason.
"The Grand Experiment": At a safe house, Sherlock believes a mole in MI6 is framing Mycroft. He's told MI6 what he knows but also said that Mycroft is the mole. He hopes this will gain MI6's confidence and while pretending to work with them to find Mycroft, that he'll find the real mole. Sherlock meets MI6 Deputy Chief, Sir James Walter and Mycroft's handler, Tim Sherrington, but is unsuccessful in gaining access to their files. He lies that he'll let them know when he finds Mycroft. Sherlock and Watson break into Julian Afkhami's store and Sherlock finds a scrambler that Afkhami could use for certain calls. Arthur West wouldn't have understood the calls but Sherlock believes he would know the date, time and location of them. At the safe house, Sherlock examines the info West had tattooed on his arms. Although burner phones would have been used by Afkhami's contact, the code of the cell tower used would be part of the metadata of the call. Sherlock realizes this is what West tattooed on his arms. As he reads the locations and dates, Mycroft confirms that he was at locations. Watson deduces that Sherrington was also there and that he is the mole. Sherlock finds that the dates correspond to events that benefited Iran and that Sherrington provided secret information to make the events occur. At the safe house, Sherlock wakes Mycroft to tell him about Watson's encounter with Sherrington and, that he knows why he re-joined MI6. He's confused why Mycroft would make such a sacrifice when he owed Sherlock nothing but Mycroft simply states they are brothers. Sherlock vows to fix the Sherrington situation. After Sherlock and Watson find evidence that Afkhami killed a man who was having an affair with his wife, Gregson tells Sherlock that Afkhami gave Sherrington up. Sherrington turns up dead and Gregson tells Bell to put out a Finest Message for Mycroft. At the Brownstone, Sherlock and Watson confront Mycroft who says he didn't murder Sherrington. He contacted NSA Agent McNally who he traded MI6 secrets for the NSA arranging for Sherrington's murder. Sherlock deduces that the NSA has faked Mycroft's death which he confirms. Mycroft will have to disappear which he tries to apologize to Watson for. She leaves, frustrated and upset. Sherlock indicates that they were working on a solution for him that would take hard work which isn't Mycroft's way. Mycroft interrupts Sherlock's chastisement by hugging him, proclaiming his love, and then leaves. Eavesdropping outside Watson's bedroom, Sherlock hears her making an appointment to view an apartment. Distressed, he retrieves a hidden stash of heroin. He then visits Sir Walter and agrees to work for MI6.