I think that the greatness of the story is that it really does not include the idea of "good" and "bad" guys. There are human beings who are capable of some fairly dark and intense elements if the conditions are right. The doctor is not a bad guy, in the broadest sense of the term. He comes there to help the girl, to protect others from infection, and to solve a medical problem. The parents are not bad, on the whole. They want their child to be healed. The girl is not bad, but rather wanting to conceal the fact that she is sick. They are not bad people, but in the alignment of circumstances and conditions, their dark sides are revealed. The parents are shown to be ineffective, at best. The girl is revealed to be an intensely driven and angry child. The doctor's sadistic element is illuminated. In the story, there are not "bad" or "good" guys, but there is the capacity for some unsightly elements to human nature that can be revealed under the right circumstances. The will to act is something that helps to bring about elements within human nature that are not necessarily representative of the "better angels of our nature." In this, Williams constructs a story where terms such as "good" and "bad" become contextual, indicating that human nature is complex and labels are not entirely effective.