Clarabel lives on a Kentucky horse farm and has a special love for the filly Glory. With the help of Chad, Clarabel can prevent Glory's sale and keep her to train her and eventually enter her for the Kentucky Derby.
Agnes Tilbee's granddaughter Clarabell (Margaret O'Brien) is excited about their Fairwood Farm's new foal, which she names Glory. Agnes (Charlotte Greenwood) is disappointed it is a filly, because the likelihood she becomes a championship racehorse is less. The farm has financial difficulties. Clarabell is attracted to wealthy Chad Chadburn (John Lupton), who allows Glory to board and train at his stable. Chad is said to be engaged to Candy Trent (Lisa Davis), a rich snob whose reckless driving in her sports car sometimes spooks the horses. Agnes can not afford to pay her feed bill, but in spite of having parted ways long ago, her former trainer, Ned Otis (Walter Brennan), pays the $50 she owes. Clarabell is heartsick when Agnes says the horse will need to be put up for auction. She enters Glory in races, but the filly is not ready and always loses. Glory also goes lame, requiring care and a long rest. A singer, Hoppy Hollis (Byron Palmer, takes an interest in Clarabell, who joins him on a song called "Glory' that becomes a success and earns them money. Agnes loses the horse in a poker game to Sobbing Sam Cooney (Hugh Sanders), who is Chad's trainer, but Chad arranges for her to win the horse back. Neighbors put up the entry fee for the Kentucky Derby so that Glory can be entered. Ned returns to train her, and Glory's surprising victory is a happy ending for all, including newly in love Clarabell and Chad, who embrace and kiss.
In Kentucky, Agnes Tilbee's Fairwood Farms horse breeding operation has been reduced to a single trailer in which she lives with her teen-aged granddaughter Clarabel (Margaret O'Brien). They have high hopes for their newest foal, but Agnes (Charlotte Greenwood) is disappointed to learn that the horse is a filly. Although a female horse has won the Kentucky Derby only once, Clarabel falls in love with the horse, which she names Glory, and plans to groom her to win the big race. Over the next months, Agnes and former trainer Ned Otis (Walter Brennan) continue to feud over who is to blame for failing to enter a horse in a derby years earlier, while Clarabel boards Glory at the neighboring stable owned by Chad Chadburn (John Lupton). Chad, who is surprised at how lovely Clarabel has become, prefers her passion for horses to his wealthy society friends's disdain for his love of the stables. Six weeks later, Agnes sets out on the annual race tour with Clarabel, trainer Joe Page (Gus Schilling), and groom Alexander (Theron Jackson). Before they leave, Chad's girlfriend, Candy Trent (Lisa Davis), scares the horses with her reckless driving and loud sports car, earning a scolding from Clarabel. At the first stop, they are joined by Ned, whom a rival owner, Grist, has hired to train his horse. Agnes dismisses him rudely, but when Ned overhears that she is having trouble paying her $50 feed bill, he presents Clarabel with a "birthday gift" of $50. Later, Clarabel learns that Agnes has put Glory up for auction in order to raise money for the farm and, horrified, races to put a stop to the sale. She interrupts the auction and is about to be thrown out when Chad and veterinarian Doc Brock (Walter Baldwin) come to her aid. As Chad breaks Glory with his own horses, Clarabel delights in the filly's speed and agility. With Fairwood Farms in desperate financial straights, Clarabel eagerly enters Glory into races, but the horse is not ready and repeatedly loses. After Agnes informs Clarabel that they cannot keep Glory, Ned offers to buy her, which prompts Agnes to decide that Glory must be worthwhile. Soon after, Chad invites Clarabel for a drive, and when Agnes sees her put on her best dress, warns her that the newspapers have announced Chad's engagement to Candy. During their ride, however, Chad assures her that the newspaper account is untrue. The next day, Chad invites Clarabel and Agnes to watch the race from his box seats, and shares their joy when Glory wins. Clarabel drops Glory off to get shod, but the horse soon disappears, and Agnes assumes that Ned has stolen her. Two young boys confess they borrowed her and got bucked off, but she soon shows up back at the farm with an injured foreleg. Months later, Glory is still lame, and Agnes can no longer afford to keep her. Certain that Glory is a champion, Clarabel enters her in the Kentucky Derby, despite the fact that she cannot raise the entrance fee. Chad invites them to dinner, where he reveals that he is going to visit Candy in California. When Candy returns to Kentucky, she flaunts a diamond ring and warns Clarabel to "run in her own class." Clarabel finds solace in singing to Glory, and when singer Hoppy Hollis (Byron Palmer) wanders in to check out his new horse, he is entranced by Clarabel's pretty voice. He insists that she join him in his nightclub act, where they popularize the song "Glory," the profits for which Clarabel donates to the stable. Hoppy soon falls in love with Clarabel and presses her to join him on tour, but she demurs. After Chad's new trainer, Sobbing Sam Cooney (Hugh Sanders), wins all of Agnes' money in a poker game, she admits to Joe that she has no choice but to close the farm and move to Brooklyn. The next day, Clarabel hears that Agnes has sold Glory to Chad, and furiously confronts Chad for having bought the horse without telling her first. Chad is dumbfounded until he realizes that Sam bought Glory without his permission, and orders the trainer to "lose" the horse back to Agnes. Sam does so in another poker game, but before Agnes can inform Clarabel, the girl packs up to go on tour with Hoppy. Agnes finds her at the nightclub, and as soon as Clarabel hears that Glory is once again hers, she returns to the farm. Agnes decides to move to Brooklyn alone, after which Clarabel hires Ned to train Glory for the Derby. They are almost defeated by the lack of the entrance fee, but all their friends band together to come up with the money, and Glory enters the race. Before the race, Clarabel tells Hoppy that if Glory loses, she will sign his contract. At the last moment, Agnes returns from New York to cheer Glory on, and all are overjoyed when the horse breaks ahead of the pack. Glory wins the race, and in the excitement, Hoppy and Candy grow attracted to each other. In the winner's circle, as Agnes and Ned make up, the announcer turns to Clarabel for a comment, but she is too busy kissing Chad to speak.
