The story is about Carol Bird, a Christmas-born child, who as a young girl is unusually loving and generous, having a positive effect on everyone with whom she comes into contact. She is the youngest member of her family and has devoted older brothers. At about the age of 5, Carol contracts an unspecified illness (possibly tuberculosis), and, by the time she is 10, she is bedridden; physicians say that she does not have long to live. The novel primarily involves Carol making plans for a Christmas celebration for the nine Ruggles children, a poor, working-class family living near the Birds. The book is a wistful moral tale about a saintly child, but is enlivened by many humorous scenes, particularly those concerning the home life of the Ruggles family.