A Certain Slant of Light

Yep. And the chilling bit about how she and Mark had already screwed up because of a child that would never be born, for the time of its begetting was past, "of their own will they are barren." (N.B.: Lewis came from a two-child family, and the two women he became involved with, admittedly when they were past childbearing, were divorced women who had had only two children each. SOMEBODY was using birth control.)