Does shock or surprise play an important role in the plot?
This is a good question. There is shock and surprise in the story. Surprise appears in two points in particular.
First, it is surprising that the story ends in the same way it began. Nothing changes. In the beginning of the story Dade is a confused young man. In the end of the story he is still a confused young man. All the advice that his father and mother gave did nothing for him. Dade is still between Star (his mother's ambitions) and Food (his father's grocery store). It is surprising that the story goes nowhere.
Second, in the climax of the story Dade decides to catch the middle-aged woman in the act of stealing. He catches her, but then he lets her go. In fact, he not only lets her go, but he also walks with her part of the way. It is surprising that he decides to catch her, and it is even more surprising that he lets her go after he has caught her. Why would he do that?