The story is told in four parts, sharply divided, differing in time, place, and characters and alternating between a Victorian country estate and a bombed-out London house during World War II. The focus of the whole is on the perception of a London woman, Mary, who learns about (or dreams) the experiences of the Victorian family and strongly identifies with Sarah, one of the daughters.

In the first episode, Papa and his family form a walking party to stroll through the stubbled autumn fields of his extensive land. The gathering honors three of his sons, who will leave the next day for boarding school. There is a sense of order and stability in their procession, a feeling of permanence. Details of action and conversation emphasize the extraordinary closeness between the two younger sisters, Henrietta and Sarah; they have shared all of their thoughts and all of their lives, and nothing, says Sarah, “can touch one without touching the other.”

The walkers are joined by two horseback riders, Papa’s eldest son and his friend Eugene. It is clear that the initiative to dismount and stroll with the others is Eugene’s, and it is clear that he is in love with Sarah. Leading his horse, he walks beside Sarah, separating her from Henrietta. Henrietta, thus isolated, begins a plaintive song that pierces her sister’s heart and makes Sarah long to call out her sister’s name and to restore the old sense of communion.

There is a sudden break. The name Henrietta is spoken not by her sister but by Mary, waking from sleep in a half-destroyed London house, in about 1942. The reader becomes aware that reality lies not in the happy autumn fields but in Mary’s mind. Somehow, perhaps through a box of old letters that she has found, Mary knows about and empathizes with Sarah’s conflicting emotions, her established love for Henrietta fighting against her awakening love for Eugene; Mary identifies with Sarah. More important, she finds the world of fifty years ago a better place to be than the present world, and she resists the effort of her fiancé, Travis, to get her out of the dangerously damaged house. They compromise: She will have two hours alone with her house and her dreams. Travis, however, takes the box with him as he leaves.

The dreamworld returns. Papa’s family is now gathered in the drawing room at the end of the day. Eugene is there, his love evident and still unspoken. When he says, “I shall be back tomorrow,” both sisters understand that he will speak then, and both are frightened of impending change. Sarah has an ominous sense that “something terrible” might happen. Henrietta promises to stay with her and protect her, and she tells Eugene imperiously, “Whatever tries to come between me and Sarah becomes nothing.” She begs Sarah to confirm that, but Sarah cannot speak.

As before, Sarah’s unspoken word awakens Mary’s consciousness; in her London world, she is aroused by a bomb falling nearby. Travis returns, anxious about her, and as she slowly returns to the war world, she speaks of the other: “I am left with a fragment torn out of a day, a day I don’t even know where or when; and now how am I to help laying that like a pattern against the poor stuff of everything else?” She wonders if she is descended from Sarah, which might explain her close identification. However, Travis has spent the two hours reading letters from the box, and he finds such a kinship impossible; the letters soon cease to mention Henrietta and Sarah, suggesting that they died young and unmarried. Another letter, written by a brother in his old age, mentions a friend who, in his youth, was killed when his horse threw him on an autumn evening after a visit to their home. In the last fine of the story, as Mary and Travis leave the London house, Travis says that the brother had always wondered “what made the horse shy in those empty fields.”