A mild-mannered milkman stumbles onto a career in the boxing ring.

Sunflower Dairy milkman Burleigh Sullivan, a failure in his job, rescues his sister Mae from two drunken boxers one night in front of a nightclub. Using a technique he developed as a child, Burleigh ducks when Spider Schultz swings at him, and Speed McFarland, a middleweight champion who is standing behind Spider, is knocked out. The incident makes national headlines and infuriates Speed's manager, Gabby Sloan, because he believes Speed's reputation is ruined. While delivering milk one night, Burleigh's horse "Agnes" collapses, so he goes to a nearby apartment and uses Polly Pringle's phone to call for a veterinarian. The next day, Burleigh and Polly meet again at a barbershop and become better acquainted. That evening, Burleigh agrees to Gabby's proposal that he fight in a boxing ring in order to raise money to save Agnes, as he was fired from his job. Burleigh trains at Gabby's retreat, but the only person who is able to teach him is Ann Westley, Gabby's girl friend. Ann teaches Burleigh to move in the ring as though he were dancing a waltz. Burleigh wins his first fight, and every fight thereafter, and becomes a national sensation and extremely egotistical, unaware that all his fights are fixed. Wilbur Austin, the head of the Sunflower Dairy, buys Burleigh's contract from Gabby for $50,000 and matches him against Speed. Polly breaks up with Burleigh because of the change in his personality. When Burleigh's horse "Little Agnes," daughter of his first horse, accidentally knocks Speed out before the fight, Spider and Gabby attempt to revive him, but Spider inadvertently gives him a sleeping potion. Burleigh manages to win this fight honestly due to Speed's condition, which is fortunate as he bet all of Speed's money on himself. In the end, Burleigh wins back his girl and gets a partnership in the Sunflower Dairy.