Can you tell me about Kaka Mahajani's skeptical friend who visited Shirdi and what happened to him?

Certainly. Chapter 35 recounts the story of Kaka Mahajani's friend, who was a devotee of the formless and averse to idol worship. He agreed to visit Shirdi out of curiosity but on two conditions: he would not bow his head to the saint, nor would he offer any Dakshina. Upon arriving at the mosque, as he set foot on the step, Sai Baba called out to him in a voice that was a perfect imitation of his deceased father's. This experience deeply moved the friend, causing him to forget his resolve and spontaneously bow his head at Baba's feet, completely astonished by what had just happened.