Mabel Mack's mother is deserted by her father and the mother dies. All that Mabel retains of her family history is a group photograph of her father, mother and herself, in a locket which she always wears. Mabel becomes a stenographer for the rich Samuel Roebuck and marries him, becoming a second mother to his little girl, who has learned to love her when visiting her father at the office. The marriage is a bitter blow to Roebuck's sister Katherine, who has been the mistress of the house since the death of his first wife. Previous to the marriage of Roebuck and Mabel, Roebuck had objected to an intimacy between Katherine and an actor named Francis Carryl. He had forbidden Katherine to have anything more to do with Carryl, and as Katherine was dependent on her brother, she has pretended to obey. After the marriage of Roebuck and Mabel, Katherine seeks in every way to humiliate Mabel on account of her uncultured ways. Mabel learns of Katherine's secret intimacy with Carryl, who desires to marry her on account of her supposed wealth. When Mabel discovers that Carryl is her own father, she realizes what a blow it will be to her husband to have his sister marry such a scoundrel and she interferes, warning Carryl not to carry out his intentions. But Katherine naturally misunderstands the evident recognition of Carryl and Mabel and is filled with jealousy and rage. She repudiates Carryl and telephones for Roebuck for the purpose of exposing his wife's supposed previous relations with Carryl. Roebuck arrives and Carryl is forced, by the group photograph, to acknowledge himself as Mabel's father. Roebuck forgives Mabel. Carryl slinks away and Katherine finding herself whipped humbly bows to the inevitable. Mabel permits her husband to think that it was she who had come to meet Carryl, her father, and that Mabel's only offense had been that she had supposed Mabel was meeting a lover and had sought to expose her. Thus Katherine's intended elopement is kept a secret and she becomes Mabel's friend.