Guilt is the driving force in Alfred's coming of age. It is guilt that first causes him to lie to Mr. Carr about the theft. When he is caught, and his mother comes to the store, it is guilt that keeps Alfred quiet. He is ashamed of his action and fearful of what could happen to him.
However, it is the guilt he feels from his mother's remonstrances that really drive Alfred to a turning point. Not only does he begin to realize the strength of his mother, but he starts to understand that his actions have had an impact on her. Not having matured yet, Alfred had not been able to see past himself to understand the feelings of others and to understand the ripple effect of his behavior. Seeing his mother alone in the kitchen, Alfred thinks:
He watched his mother, and he never spoke, but at that moment his youth seemed to be over.
His youth is over, but he is "seeing her for the first time." Readers understand that Alfred is now truly ashamed of his actions, not because of the trouble he could get in, but because of the trouble he is causing for others.