who was birdy edwards and what was his job in vermissa valley?

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.