What conflicts arise in the Walls children when their parents leave for Phoenix?

Jeannette and her siblings are forced to stay with their grandparents alone when Rex and Rose Mary decide to return to Phoenix to retrieve some of their things and to check on the house. While they are gone Erma tries to force herself onto Brian, claiming that his pants need mending. A fight ensues when Lori tries to get Erma to stop. When Rex returns and hears about the incident he is angry at the children and doesn't appear to care about what happened to Brian. His reaction causes Jeannette to wonder whether he was abused similarly as a child.