"To me, who knew his every mood and habit, his attitude and manner told their own story. He was at work again. He had risen out of his drug-created dreams and was hot upon the scent of some new problems."

This quote comes from Watson as he stands in the street looking up at Holmes's window and watching him pace quickly through his apartment. This is the first moment Watson and Holmes appear together in the story. Immediately, Watson not only reveals that he knows Holmes better than anyone, but that he is able to engage in a bit of deductive reasoning himself. Watson’s observation also introduces a tone of excitement and suspense into the story. Watson shares in Holmes’s excitement, and his curiosity and drive to solve mysteries along with Holmes are a core part of his character.

"Not a bit, Doctor. Stay where you are. I am lost without my Boswell. And this promises to be interesting. It would be a pity to miss it."

Holmes says these words to Watson after Watson declares that he should leave because Holmes's mystery client is about to show up. Holmes is referring to James Boswell, a writer who is well known for writing a biography of his mentor Samuel Johnson. Boswell often transcribed his and Johnson's conversations as well as information about Johnson's life, and these notes helped him write one of the most famous biographies of all time. Although Holmes is the main character, Watson's role as chief storyteller is just as important.