The narrator, John H. Watson, opens the novel by recounting his career as a young doctor. In 1878, after he received his MD in London, he studied to become an army surgeon. By the time he was sent to India to serve with the Fifth Northumberland Fusiliers, the second Afghan war had already begun and the regiment was now in Afghanistan. Traveling from Bombay to Candahar, he arrived in Afghanistan safely and joined his regiment as an assistant surgeon. Eventually, he was reassigned to the Royal Berkshire Regiment. With the Berkshires, he fought in the Battle of Maiwand, where he was badly injured and saved from capture only by the heroic actions of his orderly, Murray.
Doyle situates the novel during a time of violent British imperialism. Watson is just returning from the second Anglo-Afghan war, which began after the British invaded Afghanistan to prevent Russia from spreading its influence into India. Though the British were defeated at the Battle of Maiwand in 1880, they ultimately won the war, gaining territory in Afghanistan.
Watson was brought with other wounded soldiers to a hospital in Peshawar, Pakistan, where his health began to improve until he came down with enteric fever. After months of illness, Watson was sent back to England with his health in ruins and with no family or friends to rely upon. Though he had little wealth, he moved to London, among “the loungers and idlers,” living extravagantly in a hotel and “leading a comfortless, meaningless existence.” Soon, however, Watson realizes that he cannot maintain such an expensive lifestyle and decides that he must completely change his way of living.
On the same day that Watson resolves to change his lifestyle, he encounters an old colleague, Stamford, at the Criterion Bar. Though they weren’t particularly good friends, Watson is happy to see a familiar face and invites Stamford to have lunch with him at the Holborn restaurant. The two men catch up, and Watson reveals that he is looking for a less expensive but comfortable place to live. Stamford remarks that another man who was working in the hospital lab had told him earlier that day that he was seeking a roommate.
Though Watson had just decided to live his life more frugally, he is spending his time (and money) at expensive places like the Criterion and the Holborn. Watson’s delight at seeing an old acquaintance suggests that he is lonely, contributing to his sense of leading a “meaningless” life.
Excited by this news, Watson tells Stamford he would be glad to have a roommate, as he would rather not be alone. Though Stamford says Sherlock Holmes is “a decent fellow enough,” he appears wary, saying that Watson may not want to be Holmes’ roommate. He begins to describe Holmes as a man well-versed in certain branches of science, extremely knowledgeable about esoteric subjects, and at some times reserved and at other times talkative. Watson, declaring that he would prefer a roommate “of studious and quiet habits,” asks Stamford to introduce them after lunch. On the way to the hospital laboratory, Stamford and Watson discuss Holmes further. Stamford remarks that the man is “a little too scientific for my tastes—it approaches to cold-bloodedness,” and tells Watson how he once saw Holmes beating corpses with a stick to study post-mortem bruise patterns.
Watson gets his first introduction to Holmes’ many eccentricities through Stamford, whose description of Holmes as “cold-blooded” comprises a key part of Holmes’ characterization, especially in contrast to Watson’s warmth and humanity. His callous willingness to beat corpses for the sake of science is indicative of his obsession with murder, and the eclectic combination of his studies anticipates his later explanation of the “brain attic,” and its utility for his work.
Arriving at the hospital’s chemistry laboratory, Watson and Stamford are approached by a jubilant Holmes, who declares to Stamford that he has discovered a precise method to detect hemoglobin. Stamford introduces Watson to Holmes, who immediately detects that Watson has been in Afghanistan. Brushing off Watson’s astonishment, Holmes launches into an explanation and demonstration of his experiment, claiming that it is “the most practical medico-legal discovery for years,” and that it gives “an infallible test for blood stains.” Holmes claims that his discovery surpasses the old tests for detecting blood and could have been instrumental in catching hundreds of murderers who walked free. Holmes then begins to recite a list of cases in which the test could have been applied, until Stamford brings his attention to the matter at hand, explaining that Watson, like Holmes, is looking for an apartment.
Though Holmes shows himself to be extremely intelligent, he is also proud and wants an audience. He launches into a long speech and demonstration with barely an introduction to Watson, whom he has just met for the first time, and does not seem all that concerned at first with the reason for his interlocutors’ visit. Holmes demonstrates for the first time in the novel his extraordinary ability to deduce information about people, as well as his tendency to dramatically delay in explaining the reasons for his deductions.
Delighted, Holmes tells Watson he has found a place on Baker Street, and they begin to discuss their shortcomings to determine their compatibility: Holmes smokes tobacco, does chemistry experiments, and sometimes goes into long silent periods of being “in the dumps,” while Watson objects to loud noises because of shaken nerves, gets up at all hours, and is “extremely lazy.” Nevertheless, the two men agree to meet again the next day to view the apartment. Leaving the lab with Stamford, Watson wonders aloud how Holmes knew about Afghanistan. Stamford remarks that Holmes mysteriously knows things about many people, piquing Watson’s interest in his new roommate.
Despite their differences in manner and personality, Holmes and Watson seem to be complementary roommates. While Holmes appears very industrious and energetic, Watson is “extremely lazy” and becomes easily fatigued. Holmes’ long periods of being “in the dumps” are suggestive of depression, while Watson’s shaken nerves could be caused by what would become known during World War I as “shell shock” or post-traumatic stress disorder.