Who is McMurdo?

This crucial and multi-dimensional character (to whom we will refer as Douglas for the sake of clarity) could really be considered three different characters contained in one man. Introduced at the beginning of the story as John Douglas, this man appears to be a faceless victim, simply the object of Holmes’ investigation. Towards the end of Part I, however, Douglas is revealed to be very much alive, and he commences to share his history, which comprises nearly the entirety of Part II. During this “story within a story," we learn that Douglas once bore the name “Jack McMurdo," and that he was part of a notorious gang in the United States, which was not unlike the Mafia. At the end of Part II, however, we learn that “McMurdo” is really a Pinkerton detective named “Birdy Edwards." Throughout all three of his “identities," Douglas is described as fearless, intelligent, and good-humored. Douglas is an example of Conan Doyle’s skill as a writer, in that the reader is able to accept with little difficulty the composition of the “three-in-one” character.