In their farm house in a New York village, Ma Shelby prepares breakfast for her four children, Isaac, Tommy, Johnny and Susan, and then awakens them. The racket the boys make as they play and fight awakens their father, who spanks the eldest, Isaac. When a visitor chides Pa for not working, Ma sticks up for her husband, saying that he has a weak back and that he is waiting for a promised government job. At school, the teacher finds a drawing on the blackboard of Isaac kissing her. Isaac, who is "sweet" on the teacher, blames Johnny, who does not tattle on Tommy, the real culprit, and at home, Johnny receives a whipping from his father, which Ma, in tears, finally stops. Outside, Johnny's friend, Isabelle Potter, comforts him. Ma works late into the night sewing and ironing, and worries about a delinquent grocery bill. Years later, on Christmas Eve, Johnny, who now supports his parents, announces that he and Isabelle have finally become engaged. Susan and her husband, Ben Adams, a butcher, visit from New York City and bring Thomas, whose wife Phyllis has remained in the city. Isaac, now somewhat of a religious fanatic, and his wife Minnie are the last to arrive. After dinner, Pa meets two men for whom he has agreed to help transport some stolen liquor in a car that belongs to the paint company for which Johnny works. After Johnny walks Isabelle home, he hears gunshots and then sees his father drive past; Pa's cohorts have fired at some officers to create a diversion. When the car gets stuck in the snow, Johnny sends Pa home, saying that it would kill Ma if he were caught. The next morning, when Isaac brings his parents the news that Johnny is in jail and that an officer has been shot, Ma becomes hysterical and faints. Johnny, who is sentenced to three years imprisonment, urges Isabelle not to wait for him. After an upsetting dream, Pa plans to tell Ma the truth, but he dies before he can. Sometime later, Ma dreams that her family is still in the house. She is then startled to see Johnny, and he explains he has been released early for good behavior. Because he is ostracized in the small town, Johnny takes a job in Seattle and promises to send for Isabelle and Ma. Before he leaves, he arranges to mail Isaac money every month for Ma. After Isaac convinces Ma that it is best to close up the farm house, she goes to live with Thomas and Phyllis. Although Thomas invites her to stay as long as she likes, Phyllis, who is involved in an affair, objects. When Ma goes up to the roof where Phyllis is sunbathing with her lover to call her to the telephone, Phyllis berates her for snooping. After Phyllis gives her husband an ultimatum to choose between her or Ma, Ma goes to Susan and Ben, but Ben objects to her presence. Isaac, after receiving word that Johnny's engineering party is lost on an expedition to the North Pole, keeps the check sent for Ma for himself. Ma next comes to stay with Isaac, but because of Minnie's nagging, Ma goes to the poor farm, at Isaac's suggestion. When Johnny returns and learns that Ma is in the poorhouse and that Isaac did not give her the money he sent, Johnny fights him. He drags Isaac toward the poorhouse, as a crowd of townsfolk, who dislike Isaac, cheer. Isabelle finally stops Johnny by saying that it would break his mother's heart if she saw them, and Johnny sobs about his mother as Isabelle comforts him. At the poorhouse, Johnny asks a scrub woman about his mother before he realizes that she is Ma. He kicks her bucket away and carries her out, as she half sobs and half laughs. Soon, Johnny, Isabelle and Ma have fixed up the old house for Johnny and Isabelle's upcoming wedding. Although Johnny balks at inviting Isaac, Isabelle stops him from saying anything. Ma asks, "Isn't life wonderful?" as Johnny hugs them both.