Polly Vance is at a loss as to where to get the next day's food. The children scream, "Polly, put the kettle on," but she finds only a few tea leaves. The kids are disappointed when they find no jam. Polly, though only 18, has been mothering these children a long time. She enters her father's workroom, where he is poring over plans for the invention which he is confident will bring them riches. He becomes irritated when she reminds him of their poverty, and she leaves the room. She obtains a position with spinster Johanna Webb. Miss Webb's nephew, Chester Creigg, is preparing to leave home to return to college for his final year. Chester is impressed with Polly's good looks and there seems to be a mutual attraction. After some weeks Polly is overjoyed to learn that Chester is coming home. Chester has been awarded a prize at college for writing the best play. In the meantime Vance, Polly's father, has completed his invention. He takes the model to a well-known manufacturer, only to be told that the invention is already on the market. Chester has a tilt with his aunt because he will not submit to her arrangement for him to enter a bank, as he has chosen playwriting for his profession, and she disinherits him. Polly comes in with some wool and the old lady finds it is not the right color. Chester listens as the spinster scolds Polly. Polly is told to leave, and they go off together. Chester cannot convince Polly that it is the proper thing for her to allow him to help her until she gets another job. As he walks aimlessly, he is attracted by an excited crowd. He finds a man has fallen and been injured. He takes him home and has the doctor called. Polly comes home and finds Chester at her father's bedside. She is overcome with emotion at his goodness. Later Chester prevails on Polly to allow him to send her to the hospital for training as a nurse. While she is there Chester takes care of the family, though he is hard up, having sold none of his plays. On a visit to Polly's house he finds a fire started accidentally by one of the children. He is overcome by an explosion of the father's chemicals and is taken to the hospital, after risking his life in rescuing the children. One of the neighbors comes to the hospital and tells Polly she will care for the children if Polly will nurse Chester. Chester is made blind by the fire. Polly feels it is incumbent upon her to help him, so she secretly goes to the old aunt and tells her of her nephew's plight. She says that Chester has sworn not to touch a cent of hers. They hit upon the plan to tell Chester his aunt has suddenly died, leaving all her wealth to him. In this way he is brought to her old home with Polly as his nurse. Polly in the meantime has sent his finished play to a play-broker. A friend of Chester's, Pendleton, a famous oculist, comes rushing in his old boyish fashion and brings the newspaper speaking of the great new play, "Polly Put the Kettle On," and of the mystery surrounding the identity of the author. Of course, it is Chester's play, and he bemoans the fate that makes it impossible for him to see his first play. Pendleton suggests an operation. Polly takes care of the patient. Her sweet face is the first thing that greets Chester's restored vision. He is too overcome for words. But he finds the speech when he sees his aunt Johanna. Her spirit has been refined in the fires of adversity, and there is a happy reunion.