The story begins in 1881, when Dr. Watson, having returned to London after serving in the Second Anglo-Afghan War, visits the Criterion Restaurant and runs into an old friend named Stamford, who had been a dresser under him at St. Bartholomew's Hospital. Watson confides in Stamford that, due to a shoulder injury that he sustained at the Battle of Maiwand, he has been forced to leave the armed services and is now looking for a place to live. Stamford mentions that an acquaintance of his, Sherlock Holmes, is looking for someone to split the rent at a flat at 221B Baker Street, but he cautions Watson about Holmes's eccentricities. Stamford takes Watson back to St. Bartholomew's where, in a laboratory, they find Holmes experimenting with a reagent, seeking a test to detect human haemoglobin. Holmes explains the significance of bloodstains as evidence in criminal trials. After Stamford introduces Watson to Holmes, Holmes shakes Watson's hand and comments, "You have been in Afghanistan, I perceive." Though Holmes chooses not to explain why he made the comment, Watson raises the subject of their parallel quests for a place to live in London, and Holmes explains that he has found the perfect place in Baker Street. At Holmes's prompting, the two review their various shortcomings to make sure that they can live together. After seeing the rooms at 221B, they move in and grow accustomed to their new situation.