The Kindly Ones of the title are the Furies of Greek Mythology. There’s a reference to them in a painting early on, but I suspect the symbolism – if there is any – relates to the approach of the Second World War (the end of the book has Nicholas Jenkins, the narrator, managing to find a connection to provide him with an officer’s commission for the not yet exploded war).
The premonition that Widmerpool would become the villain of the novels is coming true, as he malignly scuppers some work relating to metal trading with Turkey that would have benefited England just so as to screw with a character he didn’t like.
That character was Bob Duport, the now ex-husband of Jenkins’ former lover, Jean Duport, née Templer (the sister of his school days friend, Peter Templer).
I have said before and I have said again, Jean was Jenkins’ great love. He seems scarcely to care about his wife. She is someone he married because he ought to have gotten married. But it’s the memory of Jean who keeps haunting him.
Bob reveals that she had another lover at the same time she was involved with Nicholas, and that this other man was more likely the truer focus of her affections. In fact, she left Nicholas to meet her then still husband in South American, so Bob says, because it would actually have been easier to keep carrying on with the other fellow over there. Finally, he adds that Jean is now remarried and living in Argentina.
Nicholas is clearly rocked by these revelations and I can’t but think (and also to hope) that Jean keeps reappearing in some fashion, even if only as a phantom memory.