How does the setting of the story convey what appears to take place versus what really takes place? How is contradiction shown and how does this intensify the shock?
The setting of this story gives us a picture of an idyllic village, one in which the sun is shining, the flowers blossom and the grass is green. There is a village square, there are school children playing, and there is clearly a strong community life, including square dances and Halloween programs. People are greeting one another, and catching up on the news. This is a picture of a small, beautiful village in which everyone appears to be involved in the community in positive ways.
As the story proceeds, we begin to see the horror that lies behind the peace and beauty. Our first hint, really, is the stones gathered by the boys. What are those stones for? We assume some they might be for some building project or perhaps for some youthful mischief, but we don't give those stones much thought. We are told that some of the boys have put the stones in their pockets, but, still, we don't pay much attention. We see a dad speaking sharply to his son. That can happen anywhere, but there begins to be a sense that something important and perhaps somber is taking place, particularly when we are told about the black box. (Black is seldom a good sign!) We keep reading and the ugliness begins to creep up on us, and we begin to understand that this will not end well, but we have no idea why. The final horror of this story does not really dawn upon us until the very end, when Tessie is stoned.
The contrast between the beginning paragraph and the ending paragraph is striking, and what is even more striking is how Jackson manages to get from that beginning to that ending in such a subtle way.