Based on the classic novel by Susan Coolidge, What Katy Did is a warm family drama that tells the story of Katy Carr, a headstrong, feisty 13-year-old girl. Katy's rebellious streak often challenges the patience of her widowed dad, Dr. Philip Carr, even with the help of Aunt Izzie. Katy's outlook begins to change, however, with the arrival of her ill cousin Helen, but a tragic accident confines Katy to her room, forever altering her perception of the world.