What is the main conflict in The Door in the Wall by Marguerite De Angeli?

"Hole in the Wall" is an inspiring story of hope and courage, as well as a story of overcoming disability and obstacles. As Robin, the son of a nobleman, is stricken with disease, he is forced to learn how to use his other abilities to achieve more than he ever dreamed. His struggle and success prove that the power of the mind is far greater than one can imagine.