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 wealthy Mrs. Emily 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 the sanitarium in order to convert the building into a casino. Judy hopes that Mrs. Upjohn will make a large donation and prevent that from happening.
Meanwhile, Judy's beau, singer Gil Stewart (Allan Jones), who performs in Morgan's nightclub, has spent his life's savings on a racehorse named Hi-Hat. His hope is that the horse, which he purchased from Morgan, will win a big race and the money will allow Judy to save the sanitarium. Unfortunately, he now has no money to pay for the horse's feed, and he and Tony (Chico Marx), who works for the sanitarium, and Stuffy (Harpo Marx), Hi-Hat's jockey, have to resort to trickery to fend off the Sheriff (Robert Middlemass). Tony raises some money by scamming Hackenbush in the "Tutsi Fruitsy Ice Cream" scene, in which Tony gives Hackenbush a tip on a horse, but all in code, so that Hackenbush has to buy book after book from Tony to decipher the code.
At the Sanitarium, Judy's business manager, Whitmore (Leonard Ceeley) â who is also Morgan's stooge â suspects Hackenbush is a fraud and attempts to expose him and rattle Mrs. Upjohn's faith in him by having her discover him in a compromising situation with a blonde floozie (Esther Muir). Hackenbush is saved by Stuffy and Tony, who pose as house detectives and then as paperhangers, who first paste the vamp to the wall behind layers of wallpaper and then hide her under the sofa cushions. Next, Whitmore brings in the eminent Dr. Steinberg (Sig Ruman) from Vienna, whom he hopes will expose Hackenbush as a quack.
Hackenbush, Tony, Stuffy and Gil hide out in Hi-Hat's stable, where Judy soon joins them. Whitmore finally exposes Hackenbush as a horse doctor and Morgan is about to have them arrested when Hi-Hat hears Morgan's voice and bolts, jumping several obstacles in the way. Gil realizes that Hi-Hat is a jumper, and enters him into the upcoming steeplechase race. Morgan, who witnessed Hi-Hat's jumping ability, tries to prevent him from being entered in the race. After some difficulty getting past Morgan and the Sheriff, the race begins. Knowing that Hi-Hat is afraid of Morgan, everyone works to make Hi-Hat aware of his presence before reaching the fence.[2][3][4] On the last lap, Hi-Hat and Morgan's horse wipe out; when they reach the finish line, it appears that Morgan's horse has won. Stuffy realizes that the mud-covered horses were switched after the accident, and Morgan's jockey was riding Hi-Hat in the finish, thus making Hi-Hat the winner.
Where does Judy work?
At the Sanitarium