How do the husband and wife's decisions impact their lives in a negative or tragic way?

The husband and wife are concerned about the rash of burglaries and decide that they must shore up their home and possessions against the perceived danger of the shiftless Black itinerants coming around their neighborhood. They allow this fear to become an obsession to the extent that they render their house and property ugly, inhospitable, and, eventually, deadly. They sabotage themselves; the little boy dies not because of some faceless intruder but rather because of the couple's conviction that the Black people in the area are dangerous. They do not see that their own participation in a racist society perpetuates societal unrest and poisons their own sense of morality and ability to reason.