12-year-old Katy Carr lives with her widowed father and her two brothers and three sisters in Burnet, a small midwestern town. Her father is a very busy doctor who works long hours; the children are mostly in the care of his sister Aunt Izzie, who is very particular and something of a scold. Bright, headstrong Katy can hardly avoid getting into mischief almost daily under these circumstances, but she is unfailingly remorseful afterward. She behaves somehow kind to the children and also she dreams of someday doing something "grand" with her life: painting famous pictures, saving the lives of drowning people, or leading a crusade on a white horse. She also wants to be "beautiful, of course, and good if I can." When her mother died four years earlier, Katy promised to be a little mother to her siblings: in practice, she is the kind of big sister who is sometimes impatient or cross with them, but leads them into all sorts of exciting adventures.When Cousin Helen, an invalid, comes to visit, Katy is so enchanted by her beauty and kindness that on the day of Helen's departure she resolves to model herself on Helen ever afterward. The very next day, however, Katy wakes in an ill humour, quarrels with her aunt and pushes her little sister so hard that she falls down half a dozen steps. Afterwards, sulky and miserable, Katy decides to try out the new swing in the woodshed although Aunt Izzie has forbidden it. Had Aunt Izzie actually explained that the swing was unsafe because one of the staples supporting it had cracked, "all would have been right," but she believes that children should unquestioningly obey their elders. Katy swings as high as she can and then, as she tries to graze the roof with her toes, the staple gives way. She falls hard, bruising her spine.