On a small Vermont farm in 1932, 12-year-old Lily constantly argues with her older sister, Emily. Into this combative atmosphere comes Great-Aunt Nell, who seems to understand both girls. But everything changes when in an act of revenge, Lily pushes Emily into a quarry. Soon afterward, Emily is diagnosed with polio and placed in an iron lung. Despite her intense sibling rivalry, Lily gives up what she most needs and loves -- her horse -- to help Emily, and by doing so makes a poignantly selfless gesture.