The most important theme in Nadine Gordimer's "Once Upon a Time" is Fear of "the other."
This fear can be perceived or real, and the attainment of the perfect and secure life can lead to one's own destruction.
The family's perceived fear of Black people originates from rumors and news reports which is then confirmed through reports of home invasions in their neighborhood.
When each step in their plan does not meet their need for the perfect, secure life, they take more drastic measures.
Thus, Fear of "the Other" led the family to join a neighborhood watch group, install a home security system, limiting the hours of work and location of their Black servants, and, finally, to the installation of barbed wire fencing that led to the Death of their son as he climbed it after learning about the heroic deeds of the Prince in Sleeping Beauty.
The family's wealthy status and privilege may have served as obstacles to acceptance of their neighbors.
The implication is that fear of the unknown and its associated changes seems so threatening that people will go to extremes to preserve the status quo.