If you could change one action by one character in the novel, what character and action would you choose? Why? How would your change alter the novel as a whole?

I actually would change nothing. If I wanted to change the story, and thus alter the novel, I would have Santiago give up his quest for Fatima. She, of course, would have to be a far different character, because these changes would affect everyone around them. Had Fatima refused to support Santiago, and had Santiago given everything up for her..... would have eventually torn them apart.