- "I'm a consulting detective. The only one in the world. I invented the job."
- ―Sherlock to John Watson [src]
Sherlock Holmes (born William Sherlock Scott Holmes) is the world's only consulting detective, a profession he created for himself. He is based in London and often consulted by Greg Lestrade of New Scotland Yard, usually taking his best friend and former flatmate, John Watson, on cases. He has a keen interest in unusual or bizarre crimes, without which he rapidly becomes bored, relying on nicotine to keep his brain active, although in the past he has dabbled in illegal drugs such as heroin for entertainment.
Sherlock is a thinker and an observer; his incredible ability to notice and draw deductions from seemingly trivial details is his primary tool for solving crimes he investigates. He also often utilizes his "mind palace", a tool for remembering the smallest of details and visually organizing his memories. However, his unusual and somewhat anti-social personality has led to many in the official police force distrusting and disliking him.
Sherlock claims on more than one occasion to be a "high-functioning sociopath". However, according to Jim Moriarty, as well as Sherlock's own actions and displays of emotion and empathy, this may not be true. Sherlock does not seem to exhibit any of the symptoms of an anti-social personality disorder. John jokes once, to explain Sherlock's behavior, that he might suffer from Asperger's Syndrome, a disorder on the autism spectrum, though this has never been confirmed.
- Genius-Level Intellect: Sherlock Holmes has an extremely high intellect and masterful observational skills. He is presumably the third most intelligent character on the show currently alive, with only his elder brother Mycroft and younger sister Eurus surpassing him in intelligence. However, Sherlock's intelligence was sufficient that he was able to resist Eurus's manipulation abilities.
- Deduction: Sherlock has many well-developed abilities that aid him with his detective work, including a profound aptitude for deductive reasoning.
- Investigation: He often uses a memory retrieval technique called "the method of loci", which he refers to as his 'mind palace'. John describes this system of storing memories as plotting them on a map of a familiar location and retrieving those memories by finding the way back to them, to theoretically never forget anything. To use this skill, Sherlock requires silence and space to himself to reduce outside interference.
- Cold Readings: Upon meeting a person, he will often "scan" them, using elements of their appearance and behavior to arrive at astonishingly accurate conclusions about their past or personality. He sometimes even performs cold readings on a location such as an apartment to deduce a trait related to the current resident. His cold readings are usually performed subconsciously, as his brain was still performing them and deducing things about people and places in front of him when he was heavily intoxicated on John's stag night and severely depressed after Mary's death. However, Sherlock is not infallible, as he admits "there is always something" that he misses or misinterprets.
- Espionage Abilities: Sherlock has also proven incredible espionage talents. Despite not having spoken to Irene Adler for months, Sherlock was able to follow her to Pakistan, pose as her executioner and save her life, keeping this a secret from (possibly) everyone.
- Skilled Martial Artist: He also shows great skill in both armed and unarmed combat. In reference to his Conan Doyle counterpart, the rules of the combat discipline Baritsu hang over his bed. He often uses his deductive reasoning to identify weaknesses of his opponents before he strikes them, only losing in fights when he is taken by surprise. Sherlock's unarmed skills are great enough that he was able to fight a professional assassin on even footing for an extended period of time. However, he was overpowered by John when John was angered due to the death of his wife and was no match for his mind's manifestation of Moriarty when they fought, though he was holding back with John and what happened with Moriarty was inside his head.
- "Oh, do your research. I’m not a hero- I’m a high-functioning sociopath,"
- ―Sherlock to Magnussen
Perhaps Sherlock's most noticeable trait is his proneness to boredom. He is continuously agitated by the lack of work, describing peace as "hateful". Even if a case is offered to him, he won't take it unless he finds it sufficiently attractive (though it is worth noting that he seems to lower his standards as he gets more desperate). In the absence of casework that meets his criteria, he will go to extreme lengths to keep himself occupied, such as repeatedly shooting the wall of his flat with live rounds, and even turning to drugs in more extreme situations; he claims that he is a "user" of narcotics on more than one occasion, which helps to increase his thought process. He even went so far as to accuse the criminal class of slackening, viewing that as the reason for his boredom.
Sherlock also has a blatant disregard for rules and etiquette. He once wore only a bedsheet to Buckingham Palace and was willing to walk out of there naked, greatly embarrassing Mycroft.
Sherlock has a major manipulative streak and will often take advantage of people to get his way. For example, knowing Molly has a crush on him, he will occasionally flatter her to gain access to the morgue he would not otherwise have. John, on the other hand, is sometimes subject to experiments. In one particular instance, when Sherlock needs to test out a drug, he sneaks it into John's coffee. When John tries to say "I don't take sugar," Sherlock effectively uses a 'kicked puppy' look to guilt John into finishing the drink.
He seems to have a sense of humour, though it is very sarcastic and can be quite dark. Sherlock is amused, most notably, by the stupidity of others in comparison to himself. He also often makes quips at the expense of his brother, Mycroft, usually about his dieting habits or his posh job. Sherlock is incredibly unamused; however, by John's blog. He thinks the titles John gives their cases, such as "The Geek Interpreter", or "The Speckled Blonde", are ridiculous, and he finds the fame that comes with being an 'internet phenomenon' distasteful and funny. He was also deterred by the prospect of having to wear his now-iconic deerstalker in public for the cameras. In "The Lying Detective", he puts it on before heading out to have cake for his birthday, stating "I'm Sherlock Holmes. I wear the damn hat."
One quality that Sherlock lacks entirely is tact, which is one of the main reasons that he is disliked so heavily by so many people. He often doesn't notice when his accurate deductions about other people's personal lives offend them, including the implication that Anderson and Sally Donovan were having an affair - that being said, neither of them did anything to soften his opinion of them. He is incredibly antagonistic towards the officers at Scotland Yard, particularly Anderson and Sally Donovan, which is often relayed with a cutting remark from the latter. It does seem, though that, over time, Sherlock is becoming increasingly aware of his ability to insult, occasionally asking John "Not good?" when he does see that he has upset someone.
Although he puts forth a cold-hearted and rough exterior, Sherlock does have a kind, caring side. Despite telling John that not caring about people makes it easier to do his job, Sherlock has concern for the people involved in his cases. During one of their earlier instances, when John's girlfriend Sarah was kidnapped by Chinese smugglers, Sherlock focused on saving her rather than catching the smugglers themselves and comforted her gently while untying her, even though he had not seemed to like her much previously. And again, in one of his first confrontations with Moriarty, he looks very emotionally affected when he is unable to save the life of an older woman. A bit later, at Baskerville, he tries to talk Henry down from taking his own life. He reacted with compassion towards his younger sister, Eurus Holmes, upon learning the secret behind her childhood song. When Eurus became uncommunicative following their final game at Musgrave Hall, Sherlock visited her and played his violin for her, eventually eliciting a reaction from her. He continued visiting Sherrinford and playing for Eurus over the years, later able to hold a violin recital of the two of them for their parents and Mycroft, reflecting in Eurus some measure of mental recovery and also Sherlock's dedicated care to his newly learned sister, apparently forgiving her for her responsibility of Victor Trevor's death and the subsequent trauma. He also despises criminals such as Charles Augustus Magnussen, who disgusted him more than any criminal he ever dealt with and described Culverton Smith as a monster.
Sherlock is the most protective towards the people he is close to, however. Even though it often seems like he takes Mrs Hudson for granted, he is enraged when he finds that she has been roughed up by an American operative, going so far as to tie him up and throw him out the window - so many times he "lost count". Later, when John insists that she go stay with her sister for a while, Sherlock tells him that if Mrs Hudson left Baker Street, "England would fall", while putting a comforting arm around her. This protective nature extends to all his friends, to the point that he is willing to fake his death to save them.
John and Sherlock, however, share a unique relationship. Sherlock cannot be considered a man with many friends; his attitude and cutting words often ward people away, but with John, he makes an effort. John is intelligent, though not as brilliant as Sherlock, lacking Holmes' observational skills and his unique insight into crime. John, however, does have great idea in his analysis of relationships, which Sherlock may dismiss, though often does prove to come in handy. The pair seems to have very compatible senses of humor, and Sherlock does generally appear to appreciate John's love of danger and risk-taking, even confessing to John that he "doesn't have friends. [He] just has one". He never denies it when people incorrectly assume that they are romantic partners.
When John asks Sherlock to be his best man, Sherlock is stunned into silence. He later reveals, during a very long and touching speech at the wedding, that he'd never expected to be anyone's best man because he'd "never expected to be anybody's best friend."
Sherlock shares a somewhat complicated relationship with his older brother, Mycroft Holmes. Mycroft does seem to worry a great deal about Sherlock, often rallying his younger brother's friends to ensure his safety (specifically to prevent an implied relapse), and attempting to protect Sherlock when they thought Irene Adler had died. While he does show, at times, childlike frustration with his elder brother, Sherlock never dismisses him as he does with clients or police officers he finds truly annoying or tedious. Mycroft also seems comfortable with the idea of going to Sherlock for help with issues of national security, showing once again an innate sense of trust in his younger sibling.
Though he was unaware of it, his younger sister, Eurus Holmes, had profoundly influenced Sherlock's person to the extent that, as Mycroft remarked, every choice Sherlock made, every path he ever took, the man Sherlock is, is Sherlock's memory of Eurus. When Eurus made Victor Trevor, Sherlock's childhood best friend, disappear, Sherlock was so traumatized by the loss that he rewrote his memories of Victor and Eurus, remembering Victor as his pet dog Redbeard and forgetting Eurus entirely. Mycroft noted that, because of what Eurus did, Sherlock substantially changed in personality from the emotional child he was to the cold, a deductive and logical man that he was introduced as in the series.
Irene Adler deduces that he believes in a higher power which is himself, an assertion that Sherlock neither confirmed or denied.
Sherlock runs his own website, The Science of Deduction.
Sherlock is a tall, svelte man appearing no more than in his late thirties, with pale skin and dark, curly hair. His look is designed to stand out in contrast to John, who is shorter, with straight blonde hair. His eyes can appear to be silver, blue or even green depending on the light. Sherlock's iconic outfit consists of a long ulster coat, the collar spiked up (which John calls out for being part of his "cool" image), and a dark blue scarf. Beneath his coat, he always wears a black suit with a dress shirt, no tie. During mornings in his flat, he would sometimes skip the suit jacket and instead wears a dressing gown in camel, crimson, blue or tartan. Sherlock can also be seen wearing the famous checkered deerstalker hat. He has been known, on occasion, to wear nothing but a bedsheet.
Sherlock was born on 6th January 1983 and spent his early childhood at Musgrave Hall, the Holmes family home located somewhere in the countryside. He was raised by his mother (a genius mathematician), alongside his father, who describes himself as 'something of a moron' compared to his wife . He grew up with his older brother Mycroft (seven years his senior), who Sherlock in later years claims would belittle him and try to frighten him with stories of 'the East Wind'.  He also had a younger sister named Eurus (one year his junior), who taught him the violin. 
During his early years, Sherlock befriended a boy named Victor Trevor, with whom he became 'inseparable'. The pair often played pirates together, nicknaming each other ‘Yellowbeard’ (Sherlock) and ‘Redbeard’ (Victor). Eurus harbored jealousy of Sherlock’s friendship with Victor and imprisoned Victor in a deep well, where he would ultimately die. She sang a song to Sherlock in hopes that it would lead him to her, but Sherlock misunderstood the lyrics as a set of directions that would lead him to Victor.
Eurus' animosity towards Sherlock following this led her to burn down Musgrave Hall, supposedly to kill him.
Sherlock never discovered the truth of Victor's fate and became severely traumatized, with Mycroft later claiming that he was much changed afterwards from the 'emotional child' he'd been before. To cope with the loss, Sherlock manifested a memory of owning a pet dog named Redbeard in place of his memories of Victor. As Eurus was taken away and institutionalized, his memory of her gradually faded over time. 
In 1989, Sherlock learned about the death of child athlete swimmer, Carl Powers. Upon reading that Powers' trainers were missing, Sherlock began to consider the case suspicious. He attempted to enlist the police force's help, but his attempts were denied, and the case was ultimately dismissed. 
Sherlock went to university to read chemistry but was unpopular with other students. Sebastian Wilkes, who was at university with him, later mentions how Sherlock would 'put the windup everybody' by deducing things about their private lives. 
Sherlock is said to have struggled with drugs in earlier years, at some point reaching an agreement with Mycroft that he would always write a list of anything he had taken.  It is implied that some of these struggled originated in Sherlock's trauma regarding the loss of Victor Trevor, as Mycroft has noted down 'Redbeard' from a time when he'd found Sherlock high. 
In 2004, Sherlock befriended Inspector Greg Lestrade, (after aiding him in solving a case) and through Lestrade became affiliated with the London police force with whom he maintained a rather difficult partnership with several police officers: Sally Donovan and Philip Anderson in particular distrusted him for his over-zealousness at crime scenes and harsh disposition.
At some point, Sherlock managed to gain access to St Bartholomew's Hospital, where he utilised the equipment to conduct experiments. It was here that he met pathologist Molly Hooper, who developed a secret affection for him. 
Meeting John Watson ("A Study in Pink")
Sherlock is first introduced to Dr John Watson in a laboratory at St. Bartholomew's Hospital after having been experimenting on corpses with Molly Hooper at the morgue. He shows no emotion towards the deceased, unlike Molly, who states that she knew the dead man, and thought that "he was nice". Sherlock then proceeds to beat the corpse with a riding crop to see what bruises form.
Afterwards, Molly nervously asks him out for coffee, but he misses the romantic intent of her question and gives her an order before leaving the lab. Mike Stamford then brings John Watson to meet Sherlock with the knowledge that both need a flatmate. Sherlock shows interest in John right away, deducing that he had recently been invalided home from war and that he has an alcoholic brother named Harry. Later on, when Sherlock is explaining his process of deduction, John corrects him by stating that "Harry is short for Harriet".
Shortly after meeting at 221B Baker Street, the two decide to move in together. The landlady, Mrs Hudson, offers the flat at a discounted rate because Sherlock helped ensure her ex-husband was executed for double-murder. It is also revealed that Sherlock is not good at taking care of himself, often getting Mrs Hudson to clean and bring him food, despite her arguments that she is "not his housekeeper". Shortly after, DI Greg Lestrade arrives at Baker Street and asks the detective to come to a crime scene. Sherlock is calm and collected until the Inspector leaves, when he jumps in the air with excitement, whooping "It's Christmas!" before running out the door. He returns a few seconds later, asking John if the doctor would like to accompany him.
While on their way to the crime scene, Sherlock explains how he earlier deduced personal information about John from small details about his appearance and personality, including that his limp is psychosomatic. John remarks that Sherlock is brilliant and appears visibly shocked and confused for a few moments before explaining that people usually tell him to piss off.
When they arrive at the crime scene, Sherlock insults two police officers, Anderson and DS Sally Donovan, publicly announcing that the two are sleeping together behind Anderson's wife's back. Both show apparent dislike and even hatred toward the detective. It is interesting to note that Sherlock introduced Sally as an "old friend" to John, while he openly despises Anderson to a much more intense degree.
The crime is the fourth in a series of "serial suicides", in which people are being found dead after taking poisonous pills for seemingly no reason. However, unlike the first three, this victim, a woman dressed entirely in pink, has left a note; she carved RACHE into the wooden floorboards with her fingernails. Sherlock deduces that the woman died before finishing the word, which means she was trying to cut the name RACHEL. Sherlock deduces that the woman is a serial adulterer with an unhappy marriage. Sherlock finds splashes of mud on the woman's leg, thrown up by the wheels of a suitcase, and deduces that she is from out of town. The police found no bag on the premises, but Sherlock searches for it, later finding it in a nearby skip.
He then texts John to come and send a text for him at Baker Street.
After convincing John that the killer has the phone, the two lie in wait for him at a cafe owned by a friend of Sherlock's named Angelo. However, even after the two run all over the area chasing a cab which stopped suspiciously, the lead is revealed to be a dead-end and the two return home. After laughing about the venture, they go upstairs to find DI Lestrade searching Sherlock's things for drugs. At first, John argues that there is no way Sherlock is a junkie, but Sherlock quiets him, confirming that the idea is not so far from the truth.
After much yelling and arguing, Sherlock realizes that RACHEL is the passcode for the victim's phone. She had known she was going to die and had slipped her phone to the killer, then given them the password to use the online tracker to find him. However, when they enter the password, the computer tells them the phone is in the flat. At first, Sherlock is confused but then realizes the original lead was correct, but he had questioned the wrong person. It was not the passenger in the cab that was the killer, but the driver.
He then "slips out for some air" and meets the cabbie outside. The cab driver gives him the choice of coming with him and finding out how he got those people to kill themselves or staying here, safe. Sherlock goes with him.
The cabbie brings him to a university where he ushers him inside with his gun. He then sits the detective down and brings out two pills. Stating one pill is good, the other bad, the cabbie says that Sherlock can choose whichever medicine he likes, and then the driver will take the other. Sherlock argues that it is chance, not skills that would allow him to pick the right pill, but the cabbie disagrees, calling it a "chess game with one move". The taxi driver then passes Sherlock one of the pills and asks him if it is the good or the bad one.
Sherlock deduces that for some reason, the cabbie is killing people for his children. The driver tells him of a 'sponsor' who gives him money every time he murders. He is dying, and the more money he has at the time of death, the more his children get after he is gone. After a few moments, Sherlock decided he will choose neither pill, opting instead to be shot. However, the detective grins when the cabbie pulls the trigger, revealing that Sherlock is the first to realize the gun is a fake. With no more incentive to stay, Sherlock turns to leave, but the cabbie tempts him, asking if he knows which pill is the right one.
Arrogant as always, Sherlock replies that he knows and chooses a pill, holding it above his head. The cabbie then states that Sherlock will do anything to stop being bored, even risk his life. Just as he is about to take the pill, a gunshot fires and the cabbie is hit. Sherlock demands to know if he picked right, but the cabbie merely laughs. Angered, Sherlock throws the pill on the floor and steps on the bullet hole, demanding the name of the cabbie's sponsor. The cabbie screams the name "Moriarty" just before dying.
After giving his statement, Sherlock begins to describe the traits of the cabbie's shooter to DI Lestrade: a marksman with strong moral principles and nerves of steel. However, halfway through the sentence, he spots John standing outside the police tape and realizes it was John who saved him. Quickly lying to cover for John, Sherlock states that he is in shock and needs to go home.
He compliments John on his aim, a notable act as Sherlock never compliments anybody. He then reveals the man who earlier kidnapped John is, in fact, his brother Mycroft Holmes, who works for the government. Or "as the government" as he maintains. Finally, John and Sherlock leave the crime scene grinning at each other. 
Turning down a case to find a diamond, Sherlock was attacked by the messenger while John was at the supermarket. Successfully having defeated his assailant, Sherlock gets rid of him and hides the sword used against him under his chair. Upon John's arrival, Sherlock sees he lacks any groceries; the machine refused any payment John tried. Asked for money, Sherlock tells him he has to go to the bank first, which is a big financial powerhouse. Once there, Sherlock meets his old university acquaintance, Sebastian Wilkes, who asks him for him. Just to put Sebastian off, Sherlock deduces from out of nowhere that he had made two trips around the world in the past month. Lying that he heard it from Sebastian's secretary, Sherlock subtly tells John that Sebastian's watch is two days behind. Hence he crossed the International Dateline but forgot to alter it. Sherlock was able to deduce the period this occurred in as the model of the watch was only released a few weeks earlier.
Sebastian explains someone broke into their former chairman's empty office the night before and sprayed an meaningless set of symbols on a wall and across the chairman's portrait. Shown the room, Sherlock demands to see the CCTV footage of the room; it shows the graffiti appearing between 11:33 PM and 11:34 PM, which shows the one responsible is rather quick to escape being seen. Though Sherlock declines payment for the discovery of the hole in the bank's security, John quickly accepts it on their behalf as they need money to pay their bills. Sherlock examines the room, deducing the vandal had to come through the window and that a man named Eddie Van Coon is the only person who could see the graffiti from his desk.
Leaving with John, he explains that Eddie is the only person who could see it clearly; hence it was a message to him; since he trades with China, he probably works at night, and the word was intended for someone who worked at midnight. They go to Van Coon's apartment and try buzzing him several times, only to get no response. Sherlock pretends to be Van Coon and tricks a new neighbor into letting him through their apartment, so he can use the balcony to enter Van Coon's. He soon finds Van Coon dead in his room, shot by a SIG Sauer P226 that is lying at his side.
Calling the police in, Sherlock determines from the room's contents that Van Coon had just come back from a three-day vacation, probably very recent going by the odour of his laundry. Something was also tightly packed inside his suitcase. DI Dimmock regards it as a suicide, but Sherlock points out several holes in theory – for one thing, someone appears to have inserted a black paper lotus flower into the victim's mouth postmortem. Additionally, Van Coon was shot in the right side of his head, but the victim is left-handed (as evidenced by his habits and the layout of his furniture). He explains that Van Coon had been threatened (the spray-painted message from the bank is proof of this) and was waiting for the killer. He fired a shot at the killer when he came in, and the bullet went out the open window. Sherlock advises that they should check the bullet as it did not come from Van Coon's gun.
Sherlock informs Sebastian of Van Coon's death but is berated for getting sidetracked. He next discovers a man named Brian Lukis, a freelance journalist, who was shot and killed in his locked apartment by a killer who can pass through walls. Sherlock notes that it is very similar to Van Coon's death, and gets to investigate it more.
He realizes that the murderer could climb walls, but the two victims did not know it. By locking themselves up, they thought that they were impregnable. He and John go to talk to an expert, a street graffiti artist named Raz, who identifies the type of paint, but has no idea what the cyphers represent, and agrees to make some inquiries.
Sherlock gathers Van Coon's receipts from the day he died from Van Coon's secretary Amanda, then heads to the Lucky Cat, where he meets John, who is retracing the steps of Lukis. They both realize that both victims had smuggled things from China, but something went missing. Not knowing who took it, the murderer killed both of them. Sherlock investigates Soo Lin's apartment and nearly gets choked to death.
That night, both find Soo Lin alive, hiding at the museum. However, on a reckless chase to catch the murderer, Soo Lin gets killed, and both men return home, dejected. After looking through all the books that Lukis and Van Coon both have, they still find nothing before John leaves for work. Sherlock continues through the books, suggesting to John when he comes back that they go out for some air, only to be told that John has a date.
He offers John circus tickets, but meets them there, admitting that he bought himself a third one in his name. A fight happens backstage where Sherlock discovers the murderer, before leaving after a brief struggle. Sherlock returns home with John and Sarah before going to hail a taxi. Noticing a German couple using an A–Z London guide, he takes it and solves the code, but finds John and Sarah gone.
He goes to rescue them, barely saving them from getting killed, and tries to comfort Sarah before the police arrive. 
Sherlock states, both implicitly and explicitly, that he has no friends, except for John. They live at 221B Baker Street, which they rent from Mrs Hudson at a discounted rate due to Sherlock's help in getting her husband executed. In a confrontation with Moriarty, he forces Sherlock into complying by threatening to have one of his snipers kill John. Sherlock is visibly put on the back foot by this and only rallies around at the end of the encounter when he, with John's nodded consent, threatens to blow up the bomb jacket. 
John and Sherlock's friendship continued to solidify with Sherlock announcing to John that he does not have friends, "just one". In the final confrontation with Moriarty, Sherlock fakes his death to avoid his three friends (including John) being killed. After an emotional farewell via a phone call, Sherlock jumps off of the rooftop of St Bart's while John, injured by a collision with a cyclist, stumbles towards his friend's body uttering murmurs of his complete disbelief, not realizing he survived the fall. 
John, at first, is very angry with Sherlock after faking his death for two years but forgives him and goes back to solving crimes with him.  He asks Sherlock to be his best man at his wedding. Sherlock states that he will do anything to protect John, Mary and their baby. Their friendship is stronger than ever now, with Sherlock becoming slightly more human. When he discerns that Mary is pregnant at the wedding reception, Sherlock states categorically that she and John will be the best parents in the world, as they've already had so much practice with him. 
Mrs Hudson, Sherlock's landlady, takes care of many of his needs, like washing his clothes and making food, even though she seems to do so begrudgingly. Sherlock, in turn, is protective of her – beating a man half to death after deducing that he had struck Mrs Hudson and then throwing him out of a window, claiming the man was injured when he "fell out" (several times). When Moriarty says to Sherlock he will kill "everyone you care about", the fully enumerated list comprises three names, of which Mrs Hudson is one. 
Sherlock's relationship with DI Greg Lestrade began as one of necessity, as Greg acknowledges that traditional police methods can not solve some crimes, and Sherlock needs someone to bring him in on cases.  Greg since appeared to have become someone that Sherlock would consider a friend, especially when it is revealed he is one of Moriarty's three targets designed to coerce Sherlock into "suicide". Greg can be noted as one of the few at Scotland Yard that does not completely believe, upon the evidence that Sherlock was the one committing crimes all along, that Sherlock was a fraud.  In The Final Problem, Sherlock finally has enough respect for Lestrade to get his first name right.
Sherlock and Mycroft Holmes, his older brother, have a rocky relationship at best. However, Mycroft does remark to Sherlock that they have more in common than Sherlock likes to think. There are many examples of this, one being that both of them have the exceptional brainpower and can deduce things quickly. However, there are also many examples of them being opposites of each other, as Sherlock "prefer[s] to text" and does so very frequently, while Mycroft, as Sherlock says, only texts when he cannot speak, e.g. when he is at the dentist. Despite the unstable relationship, Sherlock and Mycroft are seen to pay attention and care about each other quite a bit, knowing about each other's personal lives, and with Mycroft asking Sherlock for favours. In return, Mycroft has his way of keeping tabs on Sherlock, having a high level of national security placed on him and John. The two are seen to spend some time with each other, Sherlock having 'acquired' one of Mycroft's security cards, and when Mycroft finds out that he uses it, he is more exasperated than angry, despite Sherlock breaching a national security protocol in Mycroft's name. Mycroft later allows Sherlock access to the military base that Sherlock stole his identity to breach. Nevertheless of their arguments, Sherlock shows that he does indeed love his brother and knows him quite well, as when Mycroft tries to manipulate Sherlock into shooting him instead of John, he is able to see through the act easily and refuses to do so, even willing to sacrifice his life to save both his brother and John.
To Sherlock amusement and Mycroft's shock, their mother considers Sherlock to have always been the grown-up between the two of them.
Molly Hooper is a pathologist at St Barts Hospital and often assists Sherlock in his "experiments". She is shown to have a huge crush on him and is awkward and stuttery around him. He does not respond to her feelings for him, although he does use them to his advantage by flirting with her to get something he wants. Sherlock originally did not seem to understand how much Molly cared for him.
However, their friendship became slightly stronger. During a Christmas party at Baker Street, Sherlock upsets Molly by embarrassing her in front of everyone after he deduces that she has 'love on her mind' and is seeing someone that night. When it turns out to be him, Molly snaps back at him, standing up to him for the first time. Then, another first, Sherlock apologizes to her all on his own, much to the shock of John, and kisses her on the cheek. 
Molly seems jealous of Sherlock's "infatuation" with Irene, jumping to the conclusion that she is his girlfriend to which he questions "you think she is my girlfriend because I am x-raying her possessions?" 
Molly's and Sherlock's relationship developed substantially from colleagues into a friendship. At one point, Molly points out how sad Sherlock looks when he thinks no one else can see. He states that she can see him to which she replies that she does not count. Sherlock later tells her that she does count and that she has always counted and that he has always trusted her. When she asks what he needs, he replies with 'you'. 
Molly aided Sherlock in faking his death. To thank her, and also to temporarily replace John, Sherlock asks Molly to solve some cases with him. He also tells her that Moriarty made a mistake in believing that she did not matter to Sherlock when he admits to her that she was the one person who mattered the most. 
Sherlock asks her out for dinner "chips", but she refuses because of her engagement. When Sherlock notices that Molly is engaged, he congratulates her, saying that she deserves to be happy. He later also states how he wants her to be herself, not John, showing that he values her friendship even if he is using her as a replacement. 
Eventually, Sherlock compliments her without reason (without trying to get something) and even asks how Tom is. He also makes an effort not to say anything about the fact that Tom looks like him (hinting that Molly is not over him) showing how Sherlock has come to respect Molly and how he is starting to show regard for Molly's feelings. 
Molly was furious at Sherlock for being back on drugs, but he responds with 'sorry your engagement's over' after he notices the lack of a ring. He also has her in his mind palace when he is dying; she is shown helping him and guiding him through it, trying to keep him alive. Although it was not Molly, it shows that Sherlock has respect for her and considers her to be someone who saves his life. Unlike Irene Adler, who appears as a distraction in his mind palace, Molly appears as a motivation. It is also revealed that her house is one of his bolt holes and that she had the spare room while he had her room. 
While being tortured and put through a series of problems by Eurus Holmes, Sherlock is forced to get Molly to say "I love you" to him. Eventually Molly says it too, despite how cruel and upsetting she finds this. After this scene, Sherlock proceeds to break the coffin that was supposedly hers in a very agitated state, and screams one last time : I love you. At some point after this upsetting event she visits Sherlock and John at their flat, showing she got over it and she and Sherlock are still friends.
After Sherlock's return from the "dead", Mycroft's and Sherlock's mother and father show up at 221B, having known all along that Sherlock was alive. They appear to be very ordinary, unlike the two brothers; Sherlock tells Watson it's an embarrassment he has to deal with. It is later revealed that Sherlock's mother is a renowned mathematical genius who retired from academia to be a full-time mother.
Mummy maintains a powerful hold on both her sons, as is shown by her making Sherlock promise to stay in contact more often when both Holmes brothers are caught by their mother smoking outside of her home. When she confronts them, they hide the cigarettes behind their backs and deny they are doing anything. Sherlock even goes further, blaming Mycroft. 
Sherlock meets Janine at John and Mary's wedding and later have a short relationship with her. "Sherl", however, as she calls him, was using Janine to get access to her employer's office – Charles Augustus Magnussen. In retaliation for this betrayal, Janine sells her story to the newspapers in a "kiss and tell" story – lying about their sex life, which they'd never had. They do appear to part on good terms despite this, with Janine visiting him in hospital after he is shot (but she also lessens his morphine drip in the process--her way of avenging her "broken heart"). 
Irene Adler holds a certain fascination for Sherlock Holmes. She is shown to enjoy "the game" just as much as Sherlock, enjoying detective stories and understanding the intricacies of them similar to Sherlock. When he is first tasked to recover her phone by the monarchy, she beats him both metaphorically and literally with her riding crop, before escaping through the window, sparking a mutual fascination. When she gives him her phone as a 'Christmas present' Sherlock deduces she has been killed (it is later revealed she faked her death), and falls into a depression so deep both John and Mycroft are concerned he may begin using drugs again. However, upon learning she is alive, he recovers near immediately.
When Mycroft tells John of her capture, he states "What might we deduce about his [Sherlock's] heart?" (about how he would take the news of her death, thereby revealing that Mycroft thought that Sherlock might have cared for her, although it might have more likely been a fascination for the woman who's mind matched his own). When John goes to tell Sherlock that she went into the Witness Protection Program in America, to spare him the sorrow of learning of her death, Sherlock asks him for her phone (part of Mycroft's file on her). It is later revealed that Irene did not die in the Middle East. Sherlock infiltrated the prison to rescue her, risking his own life to save hers. 
During a later case when Sherlock is deducing who the murderer is, and is in his mind palace, he sees Irene naked (as he saw her when they first met) stroking his cheek with her hand as she smiles at him. He then tells her 'Out of my head, I'm busy', suggesting she often appears in his thoughts and he would rather she turn up later. 
In the episode "The Lying Detective" revealed that Irene continues to send SMS messages to Sherlock, and sometimes he texts to her back. John actively encourages this and seems to believe they suit one another romantically.
When asked by Eurus to 'play him' in "The Final Problem" Sherlock responds by playing the music he wrote while in mourning for Irene, known as 'Irene's Theme' or 'The Woman'. From this, Eurus deduces that Sherlock has had sex, suggesting that it is Irene Adler he has had sex with as she is the subject of the music he is playing.
Rosamund Mary Watson
Sherlock is Rosie's godfather. When John offers Sherlock to become a godfather for Rosamund, he initially refuses to do so, but he still agrees. When Mary dies, Sherlock expresses a desire to help in the education of the little Rosie, but John denies him. Later, when John and Sherlock settle their conflict, John allowed Sherlock to visit Rosie sometime. Sherlock does sometimes hold Rosie, showing he cares for her to some degree.
Eurus is Sherlock's younger sister. As children, she loved him very much and wanted to play with him. Sherlock, however, he was more interested in playing pirates with Victor Trevor. This drove her over the edge, prompting Eurus to leave Victor to drown in a well; she even attempted to kill Sherlock by burning down their home. Soon after, the trauma of Victor's death and Eurus being taken away caused Sherlock to rewrite his memories, turning Victor into a dog and Eurus into a ghost story.
In 2017, Eurus made contact with him again as Faith Smith, while he was high on drugs. She also posed as John's therapist. After being convinced to scare Mycroft senseless, Sherlock learned Eurus was insane and capable of one day gaining control of the world through reprogramming people with a conversation. When he met Eurus in her cell, Sherlock learns she taught him how to play the violin and that she got out by reprogramming the governor. She forced him through sadistic games to emotionally torture him and those close to him. Eventually, Sherlock learned the song from their childhood was a cry for love; he gave Eurus the context she yearned for. To this day, Sherlock visits her, playing the violin together in the hopes of healing her psyche.
- "We've got a serial killer on our hands. Love those; there's always something to look forward to."
- ―Sherlock to Anderson [src]
- "I'm not a psychopath, I'm a high-functioning sociopath. Anderson, do your research."
- ―Sherlock to Anderson [src]
- "Anderson, don't talk out loud. You lower the IQ of the whole street."
- ―Sherlock to Anderson [src]
- "Don't make people into heroes, John. Heroes don't exist, and if they did, I wouldn't be one of them."
- ―Sherlock to John [src]
- "Once you rule out the impossible, whatever remains, however improbable, must be true."
- ―Sherlock to John [src]
- "I don't have friends, I just have one."
- ―Sherlock to John [src]
- "Oh, I may be on the side of the angels but don't think for one second that I am one of them."
- ―Sherlock to Moriarty [src]
- "I was so alone, and I owe you so much."
- ―John to Sherlock's grave [src]
- Sherlock: "William Sherlock Scott Holmes."
- John: "Sorry?"
- Sherlock: "That’s the whole of it – if you’re looking for baby names."
- — Sherlock to John about choosing a name for John and Mary's baby.[src]
- "I'm Sherlock Holmes. I wear the damn hat."
- ―Sherlock, to John about the deerstalker
- "I am a user, not an addict. A controlled dose is not lethal, and abstinence is not immortality."
- ―Sherlock on drugs
- Sherlock takes his coffee black, with two sugars.
- Magnussen deduces that Sherlock's pressure points are "Irene Adler," "Jim Moriarty," "Redbeard," "Hounds of the Baskerville," "Opium," and "John Watson."
- Sherlock enjoys dancing and is capable of, at the very least, waltzing and a passable jazz pirouette.
- Sherlock has a Master's degree in Chemistry.
- It has been hinted by Mycroft, Irene and Moriarty that Sherlock is a virgin.
- It has been hinted by Mycroft that the two may have another sibling (in "The Lying Detective", we learn that there is a Holmes sister).
- Benedict Cumberbatch almost turned down the role.
- Benedict Cumberbatch had to lose weight to portray Sherlock.
- According to Sherlock, his mother has a lot to answer for; while he has a list, Mycroft has a file.
- Sherlock engages in daily mental exercises that involve formulating scenarios on how he would murder his friends or colleagues; for example, he has stated that he would poison John's food and suffocate Mycroft in his home.
- He changed his name to Sherlock Holmes, from William Sherlock Scott Holmes. (Whether he legally changed his name, or prefers only to use that part of his name is unknown)
- Its worth noting his mother calls him Sherlock, and Mycroft "Mikey". This could show he is favored over his brother.
- In the summer of 2011, Danny Boyle created a National Theatre production of 'Frankenstein' in which Benedict Cumberbatch and Jonny Lee Miller played the creator and monster and alternately changed nightly. Both actors then went on to play another Victorian creation, Sherlock Holmes, both set in the present day, albeit opposite side of the Atlantic.
- It is said in Sherlock: The Casebook, that Sherlock's birthdate is January 6th, 1981. On the gravestone of Sherlock birthdate revealed as January 6th, 1977.
- Though initially hating the deerstalker hat, Sherlock has accepted as his trademark.
- Observing Sherlock's behavior from A Study in Pink to The Final Problem, he has become much more "humanized" thanks to his friendship with John to the point of appearing amused by his own jokes instead of just giving deadpan one-liners.
- He has been called a "Dragonslayer" and a good man.
- He ironically shares the same self-view with Twelfth Doctor of Doctor Who.
- Neither considers themselves a hero despite their heroic actions.
- When asked about Molly's relationship with Sherlock from now on, Mark Gatiss said it was left ambiguous on purpose, probably to let the viewer interpret this as he chooses.
- Sherlock DOES text Irene back sometimes, but he largely attempts not to.
- At some point, he either told her when his birthday was, or she figured it out.
- Beneath all his cold logic, Sherlock possesses a genuine caring heart and a desire to ensure that if someone has harmed another person, they will be caught.
- Sherlock shares some similarities with The Big Bang Theory character Leonard Hofstadter in that while they are both geniuses, they are also the least intelligent person in their respective families. Also, they are both the middle child and have one brother and one sister.
- Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- Thompson, Steve; Moffat, Steven; Gatiss, Mark (writers) & McCarthy, Colm (director). (5 January, 2014). "The Sign of Three". Sherlock (2010). Series 3. Episode 2. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 January, 2012). "The Hounds of Baskerville". Sherlock (2010). Series 2. Episode 2. BBC One.
- Method of loci on Wikipedia.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 January, 2012). "The Hounds of Baskerville". Sherlock (2010). Series 2. Episode 2. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (1 January, 2012). "A Scandal in Belgravia". Sherlock (2010). Series 2. Episode 1. BBC One.
- Thompson, Steve (writer) & Lyn, Euros (director). (1 August, 2010). "The Blind Banker". Sherlock (2010). Series 1. Episode 2. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 August, 2010). "The Great Game". Sherlock (2010). Series 1. Episode 3. BBC One.
- The Lying Detective
- The Final Problem
- His Last Vow
- Many Happy Returns
- The Final Problem
- The Great Game
- The Blind Banker
- The Abominable Bride
- The Abominable Bride
- A Study In Pink
- Thompson, Steve (writer) & Haynes, Toby (director). (15 January, 2012). "The Reichenbach Fall". Sherlock (2010). Series 2. Episode 3. BBC One.
- Gatiss, Mark (writer) & Lovering, Jeremy (director). (1 January, 2014). "The Empty Hearse". Sherlock (2010). Series 3. Episode 1. BBC One.
- The Final Problem (Sherlock)
- "The Final Problem"
- Gusmaroli, Danielle (2014-02-14). "'I thought it could be cheap and cheesy': Benedict Cumberbatch reveals he almost turned down Sherlock Holmes". Daily Mail online. Retrieved 2014-05-30.
|Sherlock Holmes (Benedict Cumberbatch) • John Watson (Martin Freeman) • Mycroft Holmes (Mark Gatiss) • Jim Moriarty (Andrew Scott) • Greg Lestrade (Rupert Graves) • Molly Hooper (Louise Brealey) • Mrs Hudson (Una Stubbs)|
|Irene Adler • Mary Watson • Charles Augustus Magnussen • Eurus Holmes|
|"A Study in Pink" • "The Blind Banker" • "The Great Game"|
|"A Scandal in Belgravia" • "The Hounds of Baskerville" • "The Reichenbach Fall"|
|"The Empty Hearse" • "The Sign of Three" • "His Last Vow"|
|"The Six Thatchers" • "The Lying Detective" • "The Final Problem"|
|Unaired Pilot • "Many Happy Returns" • "The Abominable Bride"|
|"Sherlock: The Network" • Manga|