The most compelling facet of this story was Harriet - her love, her loneliness, her tenderness and her sacrifices. The regret and guilt that haunts her and the blame she suffers for actions and consequences outside of her control. As a comment on the family and on motherhood, I think Lessing has a lot to say. I’m not sure if Ben’s character could have been handled more deftly, but considering he is seen mostly from his mother’s perspective, his narration makes sense, forcing the reader as far from him as his family feels. 

Her thoughts circled in this groove. David kept saying she simply should not have gone up there, but how could she not have gone, being Harriet? And if she had not, she believed David would have. 
A scapegoat. She was the scapegoat - Harriet, the destroyer of her family.