The most standard read on this kind of question would be to center on the family members as significant or important characters in the story. I am going to go unconventional and suggest that Gordimer, herself, is the most compelling character in the story. To argue this point, I think that you have to look at the exposition of the story. Gordimer is asleep when she is startled by some sounds that, in her mind, remind her of an intruder being present. She jumps to the worst of conclusions, only to be calmed down and reassured by logical substantiation. As a character, she is rational and reasonable, not being excessively guided by fear of "the other." She accepts her own fears and her own paranoia as a part of her being, but one that cannot be the seat of all judgment and decision making capabilities. Gordimer is an important and compelling character because she represents what the family should be. Gordimer is the most compelling character in my mind because she reflects how we, as modern beings, do not have to be trapped and limited by our own fear and our own paranoia. She is a compelling character because she gives an example of how things can be and how consciousness can proceed, as opposed to the disastrous path shown by the family and their paranoia. I think that Gordimer is the most compelling character because she shows what can be as opposed to the disaster of what is when paranoia and fear are taken to their logical conclusion.