I heard Chapter 12 introduces a story about a man from Nashik. Can you tell me who he was and why he came to Shirdi?

Yes, Chapter 12 introduces a story about a ritualistic and orthodox Agnihotri (a keeper of the sacred fire) from Nashik, whose surname was Mule. His journey to Shirdi was not a planned pilgrimage to see Sai Baba. The chapter describes his arrival as a 'stroke of good fortune' and a result of his past merits. His original intention was different, but a coincidence led him to Shirdi. This unexpected visit allowed him to gain the benefit of the holy place and, as the text indicates, brought his own Guru into his sight, illustrating the mysterious ways in which a Guru's grace operates.