Kate, whose father, a university graduate, died when she was very young, is adopted by her tenement neighbor, Mrs. McMahon, after her mother, a woman of refinement, dies. At ten, the ill-nourished girl, who has grown up watching her drunken foster father fight with her overworked foster mother, goes to work in a factory after Mr. McMahon loses his job. During the next eight years, Kate's stepbrother, Big Bill McMahon, becomes her friend, sweetheart and protector.