Here are three stories in which the narrator sees into the mind of someone else.
The title story is by far the longest. Its narrator, Sarah, has attained independence in maturity, long separated from her husband and quite content, self-contained and self-aware. A sudden visit from her husband is the only event; she takes pleasure in it, and his offer of a shared holiday tempts her; she imagines the companionship 'with someone who truly understands her'. James' claim on her is possessive and patriarchal, reeking of unexamined male privilege. It's interesting but consistent that calm, intelligent Sarah, a self-identified feminist, has always accepted the inevitably narrow socially defined space for women's existence within marriage and family life.
More disturbing are Sarah's reflections on the racial/tribal similarity between herself and James; she repeatedly describes them as Vikings, closely matched physically and psychologically. This problematic thread shades into supremacy as Lessing fleshes out the description of Rose, perhaps the most important character in the story and James' second wife, who in Sarah's words is 'dark' 'duplicitous' and 'female in a basic gutter way that every decent woman hates'. She is also a Holocaust survivor. After James leaves, Sarah enters an agitated trace-like state in which she imagines how jealous Rose will react to James' illicit visit to her. She is contemptuous at first, and admits that Rose's background as a victim has always made her uncomfortable as it has restricted that contempt: this is perhaps a root of personal but 'unintentional' manifestations of racism (microaggressions) and white supremacy in UK and maybe USA: this discomfort that goes unexamined, chafing at the white mind.
This is explored in this article about the problem of terminology - rightly unresolved - white discomfort is a good thing and should be maintained to spur us into learning and action.
As Sarah enters into a deeper empathy with Rose, she thinks herself into a horrific experience, a Holocaust image, and emerges from it, now taking her rival’s perspective and taking action to help her. Thus, the point of the story is the power of imaginative, meaning-making engagement with history to precipitate the empathy that destroys prejudice, although it does not take us beyond a 'white saviour' narrative.