Dr. Hugh Loring, whose hobby is heredity, has evolved the theory that physical or mental peculiarities of children reveal the parents. The doctor's intense desire for children is only equaled by his wife's aversion. On the occasion of the doctor admonishing his wife for being friendly with an admirer she leaves him, and when her child is born she swears Ruth Carden, an employee of her husband's, who has accompanied her, to secrecy, so that she may keep from the doctor his greatest joy. Mrs. Loring dies, and Ruth returns to the doctor's office, leaving the child in the care of the nurse. Three years later the nurse finds it necessary to give up the child, and the doctor, who has fallen in love with Ruth, is stunned, for he believes that the child is hers. Dr. Loring subsequently learns that the child is his, and he and Ruth are married.