Chapter 12 seems to be setting up a story near the end. Can you tell me who the story is about and what its purpose is?

Yes, the latter part of Chapter 12 introduces an upcoming story intended to demonstrate a key spiritual principle. The story is about a man with the surname 'Mule', who is described as a "ritualistic, orthodox Agnihotri" (a keeper of the sacred fire) from the holy city of Nashik. According to the text, he was able to come to Shirdi only because of the strength of his past merits. The chapter explicitly states that this "very delightful story" serves a specific purpose: to illustrate the greatness of the Guru and to showcase the love that exists for a Guru's devotees. It sets the stage for a powerful lesson on faith and Guru-devotion.