"He has a brain of the first order. He sits motionless, like a spider in the centre of its web, but that web has a thousand radiations, and he knows well every quiver of each of them. He does little himself. He only plans. But his agents are numerous and splendidly organized." -- Holmes regarding Moriarty (FINA).

Of course, in addition to their immediate physical surroundings, Holmes and Watson had their regular interactions with other individuals. Although Holmes admits he "was never a very sociable fellow" (GLOR), he nevertheless had met with several individuals on an irregular basis, who are listed below. Watson, too, being a more sociable fellow certainly had acquaintances outside of Holmes, but in his role as case biographer, he identifies very few social relations. Many acquaintances he shared with Holmes (since, obviously, they spent a lot of time together and shared rooms).

- Mrs. Martha Hudson (the landlady)
- The Maid
- Billy, the pageboy (and, perhaps, an earlier nameless pageboy) (NOBL, YELL, NAVA)
- The short-lived (but old) terrier
- The (extremely short-lived) bull pup

Early in the annuals, Mrs. Turner (SCAN) brings Holmes a tray. Although others have surmised that the disappearing Mrs. Turner was the landlady, this was clearly the role of Mrs. Martha Hudson, a widower, who appears in so many of Watson's accounts. At various times, the suite had a maid, a pageboy named Billy (VALL, MAZA), and at least two cooks (as the "new" cook is introduced in THOR). Therefore, Mrs. Turner was probably the first cook (maids were usually younger, single women). Mrs. Hudson was either busy attending to her other duties or running her errands. It is unlikely Mrs. Turner was a different landlady who then sold the property to Mrs. Hudson; although a plausible alternative is that Mrs. Turner was a friend looking after the premises while Mrs. Hudson was traveling. It is important to note that the maid, page, and perhaps the cook probably were not employed continuously at the premises the entire time Holmes (and Watson) were there. Indeed, in NAVA, Mrs. Hudson is cooking; so either she had let her cook go or the cook was on vacation.

Family

- Mycroft Holmes
- H. Watson (deceased)
- H.W. Watson (deceased)
- Mary Morstan

Holmes had a senior brother in London (seven years older than Sherlock), named Mycroft whom he rarely saw because Mycroft "has his rails and he runs on them" (BRUC). However, Sherlock does note that Mycroft's powers of observation are superior to his own.

H. Watson was Dr. Watson's father, and H.W. was Watson's brother (both deceased). See Watson's family for further details.

Mary Morstan was the (first) wife of Dr. Watson. She died after an illness. Speculation abounds as to how many women Watson married (the highest guess appears to be five). Many scholars agree on two.

While married to Mary, Watson also had a maid and a serving girl (his wife gave notice to the latter).

Neighbors

- Dr. Anstruther
- Dr. Jackson

Watson had two colleagues who took over his practice while he was away on various errands [during his marriage(s) when he was not living at Baker Street] namely Dr. Anstruther (BOSC) and Dr. Jackson. These two doctors would have had to have lived in Watson's general vicinity in the Paddington district to serve Watson's clients in addition to their own established practices. One (or both) lived directly next door to Watson (STOC). However, it is most likely that Dr. Anstruther and Dr. Farquhar were the two elder doctors who started their practices at, relatively, the same time in adjoining houses (see STOC). Dr. Farquhar, as Watson relates, was affected by some "affliction of the nature of St. Vitus's dance," and so, he sold his practice to Watson (while his neighbor continued on). As Dr. Anstruther was also getting on in years, he must have eventually sold his practice, too. And, it is likely he sold it to the Dr. Jackson mentioned in CROO. Watson returned their assistance by taking up their practices when they were gone.

Army Acquaintances

- Colonel Hayter - Hayter came under Watson's care (either because he was wounded or for general health checkups) in Afghanistan. Hayter later took a house near Reigate, in Surrey. Holmes goes with Watson to Hayer's house to convalesce in REIG.

School Friends

- Mr. Victor Trevor - Holmes' only friend during college. They bonded during a 10-day convalescence when Holmes had been bitten by Trevor's bulldog on the ankle. Trevor's family hailed from Donnithorpe (in Norfolk) and played a significant part in the GLOR case and the beginning of Holmes' career. Trevor later moved to Terai, India in the tea-planting business.

- Mr. Reginald Musgrave - Musgrave (of Western Sussex) was only a slight acquaintance of Holmes during college, but they did know each other. Musgrave features prominently in MUSG.

- Percy "Tadpole" Phelps, a nervous, sensitive boy who went to school with Watson. They were the same age, but Percy was two forms in front of Watson. Considered by Watson to be "brilliant." Percy won scholarship to Cambridge; and his relatives were well-placed (including his uncle, who was a lord). He later went on to work for the Foreign Office and plays a central role in NAVA.

Detectives with whom Holmes Worked or who were otherwise involved in his Cases

Old Scotland Yard located at 4 Whitehall Place
(technically, the back entrance was Scotland Yard, used by visitors to see the Commissioners)

-Inspector Bardle of the Sussex Constabulary - "a steady, solid, bovine man with thoughtful eyes" (LION).

-Inspector Barton - in charge of the case of the disappearance of Mr. Neville
St Clair (TWIS).

- Inspector Baynes of the Surrey Constabulary. Watson says, "The country detective was a stout, puffy, red man, whose face was only redeemed from grossness by two extraordinarily bright eyes, almost hidden behind the heavy creases of cheek and brow." (WIST)

- Inspector Bradstreet of Scotland Yard, B Division - a tall, stout official (TWIS, BLUE, ENGI)

-Inspector Sam Brown - an Inspector assisting with looking for the Agra Treasure (SIGN).

-Inspector Dubique of the Paris Police (NAVA).

- Inspector Forbes of Scotland Yard, "a small, foxy man with a sharp but by no means amiable expression" who was "decidedly frigid" towards Holmes & Watson. He was young, inexperienced, and new to his duties (NAVA).
- Inspector Forrester of Surrey - a "smart, keen-faced young fellow" who invited Holmes to look into the matter of the murder of William Kirwan (REIG).
- Inspector Gregory - "a man who was rapidly making his name in the English detective service" and who had invited Holmes to look into the matter of Silver Blaze. Of him, Holmes said he was "an extremely competent officer. Were he but gifted with imagination he might rise to great heights in his profession." (SILV).

- Inspector Tobias Gregson of Scotland Yard - white-faced, flaxen-haired (fair-haired), fat (or at least has fat hands), gallant, and ("within his limitations") a capable officer. Described by Holmes as "the smartest of the Scotland Yarders. He and Lestrade are the pick of a bad lot. They are both quick and energetic, but conventional - shockingly so. They have their knives into one another, too. They are as jealous as a pair of professional beauties." (STUD, SIGN, GREE, WIST, REDC).

- Inspector Hill - A Scotland Yard Inspector whose specialty is the Italian Quarter and Saffron Hill. It was he who identified the dead Pietro Venucci (SIXN).

- Inspector Stanley Hopkins of Scotland Yard - He was a "young police inspector for whose future Holmes had high hopes," but Holmes later says "Stanley Hopkins' methods do not commend themselves to me. I am disappointed in Stanley Hopkins. I had hoped for better things from him" (BLAC, GOLD, ABBE).
- Inspector Athelney Jones of Scotland Yard - A well-known and "energetic" detective (SIGN).

- Mr. Peter Jones, Police Agent of Scotland Yard (may be the same as Athelney Jones): bulky and described by Holmes as "an absolute imbecile in his profession. He has one positive virtue. He is as brave as a bulldog, and as tenacious as a lobster if he gets his claws upon anyone" (REDH).

- Inspector Lanner of Scotland Yard who appears only once but Holmes obviously knows him from other investigations (RESI).

- Inspector Lestrade of Scotland Yard who is variously described as: sallow, rat-faced, dark-eyed, conventional, obtuse, resolute, quick, energetic, jealous, dapper, small & wiry bulldog, lean, ferret-like, furtive, sly-looking (STUD, HOUN, BOSC, NOBL, CARD, EMPT, NORW, CHAR, SIXN, SECO, BRUC, LADY, 3GAR). Holmes comes to be on good enough terms with Lestrade to offer him spirits and a cigar when he comes to discuss a case in NOBL (although, it is worth noting that in the same interview, Holmes verbally ill treats Lestrade because of his detecting blunders).

- Inspector Alec MacDonald of Scotland Yard who later achieved national fame. He was a young, trusted, and distinguished Scotsman originally of Aberdeen. Watson describes him: "His tall, bony figure gave promise of exceptional physical strength, while his great cranium and deep-set, lustrous eyes spoke no less clearly of the keen intelligence which twinkled out from behind his bushy eyebrows. He was a silent, precise man, with a dour nature and a hard Aberdonian accent." Holmes addresses him as "Mr. Mac." (VALL)

-Inspector MacKinnon - a "smart young police inspector" of Scotland Yard (RETI).

-Inspector Martin - "A dapper little man, with a quick, alert manner and a waxed moustache." He was a "trim" country inspector from the Norfolk Constabulary (DANC).

-Inspector Merivale of Scotland Yard who asked Holmes to look into the St. Pancras
case (SHOS).

-Inspector Montgomery of Scotland Yard who took the testimony of Jim Browner at the Shadwell Police Station (CARD).

- Inspector Morton of Scotland Yard - an old acquaintance of Holmes and Watson, he aided Holmes catching the murderer of Victor Savage. Dresses in unofficial tweeds (DYIN).

- Inspector Patterson of London, who was assisted by Holmes in the matter of catching Moriarty's gang. He had a secret drop with Holmes called "pigeonhole M."

- Fritz von Waldbaum (a well-known "specialist" of Dantzig) (NAVA).

- Inspector Youghal of the Criminal Investigation Department (C.I.D.), which, incidentally was sent up in 1878. (MAZA)

Unofficial Assistants of Holmes

- Cartwright (14 years old) works at the District Messenger's Office and sometimes assists Holmes when called upon such as delivering food to a incognito Holmes on the moor (HOUN).

- Wiggins (the leader) and the other (roughly 6) street Arabs (including one named Simpson) that make up the "Baker Street Division of the Detective Police Force" or the "Baker Street Irregulars" (STUD, SIGN) also known as the "Baker Street boys" (CROO). In CROO, Holmes notes that he has "one of my Baker Street boys [Simpson] mounting guard over [Corporal Henry Wood] who would stick to [Wood] like a burr, go where he might."

Watson's Early Acquaintances

- Mr. Murray - Watson's devoted and courageous orderly (in the 2nd Afghan War) "who threw [Watson] across a packhorse, and succeeded in bringing [him] safely to the British lines" (SIGN).

Mutual Acquaintances

- Mr. Stamford, who had been a dresser under Watson at Barts and who passed intermittently through the hospital laboratory, introduced Watson and Holmes when they were both searching for someone to share rooms (STUD).

Arch Enemies

- Dr. James Moriarty - of good birth and excellent education, with a "phenomenal mathematical faculty. At the age of 21 he wrote a treatise upon the Binomial Theorem" (FINA). He had a brother who survived him, Colonel James Moriarty. Dr. Moriarty had diabolical hereditary tendencies, as a criminal strain ran in the blood. He had "extraordinary mental powers" according to Holmes. He resigned his mathematical chair at a small university in London after rumours spread. He went on to become a tutor for Army candidates. He was the "Napoleon of crime." He organized "half that is evil and nearly all that is undetected" in London. He had many, well-organized agents to carry out his careful planning. In appearance, he was clean-shaven, pale, ascetic-looking, with rounded shoulders from study and puckered eyes. "His face protrudes forward and is forever slowly oscillating from side to side in a curiously reptilian fashion." He carries a memorandum book with him.

Information on Scotland Yard from Metropolitan Police History.