Maggie O'Farrell tells both of those stories here. In bits and pieces we learn of Esme's childhood in India and her life as a young woman when she and her family move back to Scotland. We learn what led up to her institutionalization, and we learn some of what happened to her while she was there. But more important we learn that she stayed in the institution for more than 60 years, that her sister never let on that she was there, so that when the institution was to close, her mere existence was a great shock to her only relative.
I had a bit of a hard time getting into this story, since the writing is a little stilted at first, but soon the story itself drew me in. What actually happened that got Esme committed? Will Iris take her in? What role did Esme's older sister Kitty have in her commitment? And what is the biggest secret of all (because you know there is one)? O'Farrell answers all these questions expertly.