Meek Erwin Trowbridge (Frank McHugh) finally has enough of his sneering brother-in-law, Clarence Dobbins (Paul Harvey), unappreciative boss, greeting card publisher J.G. Carver (Guy Kibbee), and the lack of support of his wife Audrey (Carol Hughes). Erwin goes on a drinking binge and ends up in a hotel bar.
The film is a silent character sketch that shows Chimmie Hicks (Charles E. Grapewin) imitating a man at the races winning and losing. Filmed on a bare stage with a dark backdrop, the sketch captures Chimmie in a three-piece suit and overcoat holding a racing program while watching a race taking place offstage. It shows him excitedly jumping and pantomiming that his horse has won the race. A second man enters the frame and gives Chimmie his winnings. Chimmie returns a sum of money to the booker to place another bet. The next race begins and Chimmie again shows great excitement, which quickly turns to despair and anger as the horse loses. The bookie returns, collects all of Chimmie's money and his watch. The gambler falls to his knees, shakes his arms toward the sky, and tears up his racing form, scattering the pieces on the ground. He rises and sadly begins to leave the stage.
Al Jolson plays Gus, a loyal stable boy and jockey to a rich family in the South that has been interested in horse racing and breeding horses for generations. (In a flashback we see Jolson's grandfather, who also worked for the same family back in 1870.) The young heir of the family, Jack, loses a lot of money by gambling and is blackmailed by the crooks he lost to for forging a check. They convince Jack to ask his mother to replace Gus with another jockey for the family's racehorse, "Big Boy", but she refuses. The crooks frame Gus and he is discharged for tampering with the horse. Gus is replaced by a jockey who has been bought off to lose on purpose. Gus find works as a waiter in a fancy restaurant. While working there he uncovers the details about the race throwing plot and he reveals this to Hughes and then, with his help, outsmarts the crooks just in time to then ride "Big Boy" to victory.
During the Civil War, Thad Goodwin (Charles Waldron) of Elmtree Farm, a local horse breeder resists Capt. John Dillon (Douglass Dumbrille) and a company of Union soldiers confiscating his prize horses. He is killed by Dillon and his youngest son Peter (Bobs Watson) cries at the soldiers riding away with the horses.
Henry Sharon is about to be ruined financially by rival stable owner Lew Ralston when he gets an idea to fake his own death. His prize horse Certified Check is bequeathed to niece Martha, a young woman Ralston had hoped to marry.
Terry is a teenaged girl whose Uncle Willy, a horse trainer, dreams of winning the Derby. He bets everything on his horse Sunset, then collapses and dies after it loses.
Hugo Z. Hackenbush (Groucho Marx) is a veterinarian who is hired as chief of staff for the Standish Sanitarium, owned by Judy Standish (Maureen O'Sullivan), at the insistence of her most important patient, the rich Mrs. Upjohn, (Margaret Dumont), who insists on being treated only by Dr. Hackenbush. The Sanitarium has fallen on hard times, and banker J.D. Morgan (Douglas Dumbrille) is attempting to gain control of it. Judy hopes that Mrs. Upjohn will make a large donation and stop that from happening.
Horse racing enthusiast T.H. "Randy" Randall is a happily divorced man nowadays. On the day of the one-year anniversary of the divorce, he and his former wife, Valerie, go to the restaurant where they first fell in love. Randy was responsible for breaking up their marriage in the first place, by spending more time with his race horse than Valerie. At the restaurant, while they are dancing, the police come and arrest Randy for not paying his alimony to Valerie. He is thrown in jail, and desperate to get out he starts to plan how to get rid of his obligation to pay alimony altogether. He finds that the best solution is to get Valerie to marry someone else, and so he tries to fix her up with a friend of his, Paul Hunter. They both accompany Randy to a party at the estate of a rich eccentric socialité, Ethel Hilary, who has a special interest in collecting original characters to her circle of friends at the estate. Besides Randy and his company and yoga master Dickie Brown, a very handsome man named Freddie arrives to the estate. He is unknown to everyone, but is soon romantically interested in Valerie, trying to get her interested in him by singing her a serenade in the night. She mistakes the singer for Randy, and he discovers that Valerie is more interested in Freddie than Paul, and forces her to go with him instead of Freddie to a picnic. Problems arise when Randy gets a flat tire and Valerie has to be escorted by Freddie anyway. She manages to get Freddie to propose to her at the picnic, but is devastated to learn that Freddie is already married. Having re-discovered his interest in Valerie, Randy gets jealous of Freddie, and wants to remarry his ex-wife. Randy quickly proposes to Valerie and she immediately accepts, having longed a long time for him to utter those words. Unfortunately Randy's lawyer, Bill Carter, accidentally reveals that Randy has had a "plan" to get rid of the alimony, and Valerie gets second thoughts about marrying him again. She decides on marrying the dull Paul instead, upset with Randy's presumptious behavior. The marriage is about to take place at the estate, but on the wedding day both Randy and Paul turn up as grooms. During the ceremony, Randy's own race horse Ajax participates in a race broadcast over the radio. The ceremony is quite disturbed by the race, and just when Valerie has decided to marry Randy, the horse wins the race to both their joy.
Sorrowful Jones is a New York bookie who keeps his operation hidden behind a trap door in a Broadway barber shop. He suffers from a financial setback when a horse named Dreamy Joe, owned by gangster Big Steve Holloway, unexpectedly wins a race. Jones has to pay all the many customers betting on the horse to win, which empties his pockets completely.