Wilson is the manager of the messenger service in Chapter 4 where Cartwright, Holmes' temporary kid assistant, works. Wilson is loyal to Holmes because Holmes helped to save his "good name, and perhaps [his] life" (4.112). How did Holmes save Wilson? We don't know, and it doesn't really seem to matter. Wilson is present in the novel for just a few sentences, but he gives us the sense that London is full of stories about Holmes and his adventures.