Twelve-year-old Katy is constantly making and quickly breaking resolutions about how she will change her ways and treat others, especially her five younger brothers and sisters, with more respect and compassion. When Katy meets her Cousin Helen, an invalid, Katy is awed by her kindness, prettiness, and generosity. Katy is determined to become more like Helen, a resolution that lasts only a few hours. Soon, however, Katy gets a chance to become more like cousin Helen than she ever wished as she finds herself confined to her bedroom for four years as a result of an accident. Much of the story is focused on the change Katy undergoes during her illness. Helen visits again to advise Katy to learn from her experience and to try to become the center of the house by making her room and herself more attractive to others. One way Katy decides to take Helen's advice is through assuming the responsibility of running the house, a job that consists of giving the servants instructions and ringing her bell to summon her sisters when she has a task for them. As soon as Katy has learned the lesson about how to care for others, she recovers and regains the ability to walk.