Lucy, with the mind of a five-year-old, lives with her mother-in-law, Dorothy Hayes, and son, Luke Hayes. Luke gives up his career to return home and support his mother. When Dorothy Hayes asks the matchmaker about matchmaking for Lucy, she cries and insists on staying to care for her son, moving Luke to promise he will never leave. Luke always defends her, whether she is blamed by neighbors for ruining crops or when Lucy brings an umbrella for her son in the rain, slips, and is bullied by Clyde before Luke intervenes. Even when Grandfather Chester Hayes scolds Luke for sacrificing his future, Lucy secretly saves yams for her hungry son. When Luke loses his diploma, Clyde torments Lucy, who almost kneels for her son before fighting back. Eventually, Luke succeeds in business, helps his mother get treated, and resolves all family misunderstandings.
