In New Orleans, racetrack gambler Salty O'Rourke gets into trouble with gangster Doc Baxter, "the Bookmaker," when Salty's partner runs off with Baxter's $20,000 and is consequently murdered. Baxter gives Salty thirty days to come up with the money. Salty hocks his expensive cufflinks and buys a hot-tempered horse named "Whipper," with plans to win the Delington Handicap in California. Salty recruits twenty-one-year-old Johnny Cate, who is hiding out in Mexico after being banned from racing for fixing a race. Posing as his seventeen-year-old brother Timothy, Johnny arrives with Salty and his trainer, Smitty, in Delington, where Johnny is forced to attend jockey school. The beautiful young teacher, Barbara Brooks, expels Johnny immediately for his "fresh" mouth and insolence, but Salty gets him back in school by befriending Barbara and her mother. Although Johnny becomes infatuated with Barbara, she falls in love with Salty, who is only interested in winning the race. At Salty's request, Barbara invites Johnny to her house for individual tutoring and tries to reform him. She then chooses Johnny as her escort for the jockey ball the night before the race, and at the ball, Johnny proposes to her. She gently turns him down in favor of Salty, and Johnny vows revenge against him. Barbara accuses Salty of using her and tearfully confesses her love to him, causing Salty to take notice of her for the first time. Meanwhile, Baxter, who has arrived in town, makes a deal with Johnny to double-cross Salty. At the track the next day, Smitty's friend Tony tells him that he saw Johnny and Baxter together at the steambaths, and Salty confronts Johnny, appealing to his better side. Salty confesses his love to Barbara before the race, but tells her to say good-bye, as he will be running from Baxter following the race. Johnny has a change of heart halfway through the race, and Whipper wins. Baxter's henchman shoots Johnny dead in the racetrack's parking lot. Before confronting Baxter, Salty drops off Barbara, who steals his gun. In Baxter's office, Salty knocks out the light, and because Baxter and his henchman inadvertently shoot each other, Salty avoids a murder charge. Later, as Smitty drives Barbara and Salty out of town, she returns his gun, which he discards, then kisses her.
