Dr Watson returns to England from the Second Anglo-Afghan War. He saves money on an apartment by getting a roommate who turns out to be Sherlock Holmes. When Watson finds out Holmes is a detective he starts to follow him on his cases and write down everything Holmes does. Dr Watson is the narrator of all the stories except one.
In The Hound of the Baskervilles, Watson shows that he has picked up some of Holmes's skills at getting information from people. He observes to the reader, "I have not lived for years with Sherlock Holmes for nothing".