Once Upon A Time by Nadine Gordimer brings the fear of the unknown (the main theme) into the lives of her readers and into their dreams while the tragedy of a family's efforts to protect itself unfolds. This fear causes the family to take extraordinary measures and to intensify its security to the point where the family is no longer aware of what it is that threatens it so much or what it needs protection from. By using various comparisons, Gordimer is able to create images for the reader which reinforce the theme.
To show her own vulnerability and susceptibility to unknown forces even without any irrational fear, Gordimer uses simile when she compares her windows which have no burglar-proofing to a thin layer of frost and (a second simile) even as having the potential to shatter as she says her own "windowpanes are thin as rime, could shatter like a wineglass." Gordimer justifies the fear by telling the reader about a recent murder in her neighborhood. The difference for the narrator though is that she can explain her fear and then manage it; something the family cannot do.
The family which is living "happily ever after" is unable to enjoy its home because it seems that there is always another threat. It is ironic that the family does not choose the "twelve-inch spikes" as the next measure of protection but rather an even deadlier barbed wire which the narrator compares to some unnamed creature with "fangs." This comparison is a metaphor and is significant because it is the barbed wire which attracts the little boy and sparks his imagination and it is the same barbed wire which becomes almost animal-like and which causes the tragedy. Gordimer continues to use metaphor when describing the barbed wire as a "cornice of razor thorns" which surrounds the house and which creates a striking visual image for the reader. For the little boy, the wire is "a shining coiled tunnel" (metaphor) and is irresistible. This develops the theme significantly as the unknown fear is also unseen but unfortunately, this family is unable to see beyond their own limited perspective. This makes the wall symbolic and reveals the contradiction. The wall has the capacity to keep undesirable elements out but it also masks the real problem.
Soon after the little boy becomes nothing more than a "bleeding mass" (metaphor) and the parents' greatest fear is realized. However, it is not anything they could have planned for or anticipated. Had they spent more time enjoying their little boy rather than concentrating on their paranoia, perhaps the tragedy could have been avoided.
She compares things without using like or as.