Aside from the fact that Polly had red hair in abundance, she was not otherwise an exceptional child, save for one thing. She was willing to work and slave, if need be, to keep her baby brother, affectionately termed "The Lump," from being sent to the poor house. So she did housework and prepared breakfasts for John Ruffin, an attorney, and Hon. Gedge-Tompkins. John Ruffin's sister, Lady Osterly, has separated from her husband, and he holds their child. When Lady Osterly calls on Ruffin she is struck with the remarkable resemblance Polly bears to her own child. Ruffin and Lady Osterly formulate a plan to come into possession of her daughter, by using Polly as a substitute. When they offer Polly twenty sovereigns to go to the Duke of Osterly's home and impersonate the other child, the amount of money fairly staggers Polly and she accepts. By changing the children when the child of the Osterly's is out riding with her nurse. Polly gains access to the Duke's home and the Osterly child comes to John Ruffin's apartments to stay until her mother can get her ticketed to the continent and travel away with her. Polly does the best she can under strange conditions, but despite her resemblance to the Osterly child, the servants are suspicious and the Duke falls to wondering what has happened. Young Lord Ronald, visiting the Duke, is above all suspicious of Polly. The Osterly girl is under similar suspicion at Ruffin's home. "The Lump" positively declines to have anything to do with her. There is a blunder in the preparations Lady Osterly and John Ruffin make for the European trip. Polly disregards positive instructions and leaves the Osterly mansion before plans can be worked out. The Duke follows Polly in his automobile, searching for her in a nearby park where she has liked to go with young Lord Ronald to play. Finding Polly where he thought he would the Duke carries her back to his home. Here John Ruffin directly arrives, to tell the Duke that his wife and child must, by that time, be well on their way across the Channel. Lady Osterly, through miscalculation, has become worried because Ruffin does not arrive with the tickets and telephones him at the Duke's (her husband's) home. The servants call the Duke in answer to the summons and thus husband and wife find themselves talking to each other, much to their mutual surprise, as well as secret delight. As a result of this accidental 'phone call, a reconciliation is effected and everything ends happily for everybody, including Polly Redhead, who has made a great conquest of young Lord Ronald's heart.—Moving Picture World synopsis

Twelve-year-old Polly must support her little brother Edgar, and she works as a maid in the home of attorney John Ruffin. Polly wins Ruffin's sympathy because she resembles Marion, the daughter of his fiancee's sister, Lady Osterley, who is separated from her husband, the duke. Knowing that Lady Osterley is unhappy because the duke insists upon sole custody of Marion, Ruffin conceives of the plan to substitute Polly for Marion. The switch is accomplished and Marion runs away with her mother. After several misadventures, the duke and Lady Osterley are finally reconciled, and Polly finds a happy home as well.—Pamela Short