Narrator John Watson explains his academic and military career. After studying to become a surgeon for the army, he served in the Second Anglo-Afghan War. During a battle the British lost, he was shot in the shoulder and forced from the front lines. His condition was severe enough that he was discharged and returned to England in hopes of improving his health.

Finding it difficult to live in London on his modest income, Watson looks for a roommate. A former colleague connects him with a man named Sherlock Holmes, but not before warning him of Holmes’s eccentricities. They meet in the chemical laboratory of a hospital, where, without any introduction, Holmes exclaims that he has discovered a way to reliably test blood stains, brags about how significant it will be in criminal cases, and demonstrates a remarkable knowledge of legal history. Holmes also surprises Watson by deducing that Watson has been in Afghanistan.

After sharing their respective vices and shortcomings to ensure neither will find the other intolerable, they agree that the match seems well-suited. Holmes has his eye on a suite in Baker Street and they arrange to meet there the next day to have a look at the place.