A fight manager decides his client needs a family for publicity purposes.

After selling off twice his actual stake in fighter Curley Bender, fast-talking boxing manager Billy Murphy, his wily sweetheart, Doris Harvey, and his assistant, Eddie Black, leave town to scour the countryside for a new boxer to manage. Their search takes them to Kokomo, Indiana, where they discover the talents of Homer Baston, an orphan left on the doorstep of two old men more than twenty years previously with a note from his mother promising to return. Homer rejects Billy's offer to go on the road and fight professionally and insists on waiting in Kokomo for his mother to return. After failing to entice Homer with the promise of winning a million dollars, Billy and Doris manage to convince him that touring the country as a fighter will increase his chances of finding his mother. However, when Homer becomes homesick for Kokomo and decides to leave them, Billy and Doris trick him into believing that his mother has contacted them with news of her plans to join her son. To prove it, Billy shows Homer a picture of James Whistler's painting "Portrait of My Mother," and the gullible orphan says that she is everything he thought she would be. Faced with the problem of actually having to produce a mother for Homer, Billy finds an old, drunken kleptomaniac, Maggie Manell, at the courthouse. After paying her bail and promising Judge Bronson to care for her, Billy dresses her up to look like the "Mother" in Whistler's portrait and takes her to meet her long lost son. Homer immediately takes to Maggie, but the plan backfires when he announces that he no longer needs to box now that he has found his mother. After learning that a great deal of prize money is at stake, Maggie encourages her son to fight and quickly takes over the management of his finances. Meanwhile, Homer becomes enamoured with Marian Bronson, a reporter. Maggie soon squanders all of Homer's winnings as he punches his way to the championship, but Doris and Billy devise a plan to stop her by bringing in her ex-lover, jailbird Muscles Malone, and paying him to tell Homer the truth about Maggie. Unfortunately, their plans fail when Maggie introduces Muscles to Homer as his father and Muscles goes along with the ruse. After setting their engagement, Marian and Homer throw a dinner party so that his parents can meet her parents. When Maggie and Muscles realize that Marian's father is the judge who handled their cases, they try to flee, but Billy and Doris stop them. Later, when Maggie gets into trouble with some racketeers for writing a bad check, she and Muscles try to avoid being arrested by convincing Homer to take a dive in the championship fight against Curley Bender and fix the fight in favor of the racketeers. Eventually, Maggie becomes troubled by all the lies that Homer has been told and tells him the truth about her. Homer refuses to accept the truth and believes that she is merely behaving as any selfless mother would when her son is in a fix. Though he had intended to lose the fight, Homer knocks out Curley when Curley insults his mother, and Homer is announced the winner. In retribution, the racketeers tie up Homer and Muscles, but the two manage to escape when a blustering fight between Maggie's strongmen and the racketeers ensues. All ends happily when Homer decides to adopt Maggie and Muscles as his parents, and when the judge marries Homer to Marian and Muscles to Maggie.