What is the reason the narrator is afraid?

A first-person narrator, implied to be Gordimer herself, begins the short story by commenting in a rather disdainful way that someone once told her all authors should write a story for children; she is not interested in doing so. This changes one night when she is awakened by the fear that someone is inside her house. After she realizes that what she hears is just the house settling, she begins to tell herself a “bedtime story.” These innocuous words belie the disturbing nature of what she was just remembering—a neighbor who was murdered in broad daylight and another who was knifed, his dogs strangled—and what she was just thinking about in terms of her house—that it is essentially built on “undermined ground,” ground that may house migrant miners “interred in the most profound of tombs.” Gordimer makes it clear right away with her murdered neighbors and buried-alive South African Black miners that this is probably not going to be a “bedtime story” that would comfort a child.