I read about a friend of Kaka Mahajani who was skeptical of saints. Can you tell me the full story of his visit to Shirdi and his interaction with Sai Baba concerning his vows?

Certainly. Chapter 35 details this incident involving Kaka Mahajani's skeptical friend, who was a devotee of the formless and averse to idol worship. He agreed to go to Shirdi from Mumbai under two conditions: he would not bow his head to the saint, and he would not offer any Dakshina. When they arrived at the mosque, Sai Baba immediately saw the friend and called out in a tone that was a perfect imitation of the friend's late father. This astonishing event caused the man to forget his vow and bow at Baba's feet. Later, Baba asked Kaka Mahajani for Dakshina on two separate occasions but completely ignored the friend in this regard. This deliberate omission left the friend feeling restless, demonstrating how Baba addressed both of his challenges in a unique and transformative manner.