What is the overarching theme and message conveyed through the narrative in Chapter 34?

The central theme of Chapter 34 is the supreme glory and healing efficacy of Sai Baba's Udi, especially in situations where conventional and medical remedies have utterly failed. The chapter opens by stating it will continue the narration on Udi's greatness and uses the story of the doctor's nephew as a powerful illustration. This narrative, described in Chapter 34 as being based on experience, shows that even a "most difficult and extraordinary malady" like a bone-cyst, which resisted all native, foreign, and surgical treatments, could be addressed by the Guru's grace. The message is that unwavering faith and seeking refuge in the Guru can provide a path to healing and solace, even when all other hopes are exhausted.