After reading the letters and getting into the first few chapters, I noticed a connection between Victor and the stranger Robert Walton meets. They both talk about their tainted destinies (the stranger refers to his past as being dark and disastrous. As Victor tells about his childhood, he begins to hint at parts that led to his downfall. He describes them as an unavoidable force of evil nature that was waiting to come a get him. I believe that the stranger and Victor are the same person and where the letters leave off make this quite plausible.