“As a rule,” said Holmes, “the more bizarre a thing is the less mysterious it proves to be. It is your commonplace, featureless crimes which are really puzzling, just as a commonplace face is the most difficult to identify.”

Sherlock Holmes’s remark after hearing Jabez Wilson’s story highlights one of the central themes of the story: the connection between the bizarre and mundane. Holmes claims that what appears to be the strangest, most out-of-the-ordinary occurrence can actually be explained through simple means. The Red-Headed League and Jabez Wilson’s story, for example, prompt Watson and readers to expect a complicated explanation for such a confusing scenario. The truth, however, is far simpler, as Holmes reveals that John Clay concocted the whole Red-Headed League scheme to assist a common bank robbery. What’s more, Holmes declares that even though he can solve this seemingly bizarre case, the incomprehensible crimes are the ones that people see and hear about every day. In other words, Doyle suggests that although a great mind like Holmes’s can penetrate the rare bizarre cases, nothing seems to be able to explain the fact that we live in a world in which crime itself is, as Holmes says, “commonplace.”