The Marx brothers try to save the circus for its young owner by getting a performance at a high-society party.
In the circus of young Jeff Wilson (Kenny Baker) Julie Randall (Florence Rice) sings "Step Up and Take a Bow." John Carter (James Burke) tells his partner Jeff he must pay him $10,000 by Saturday, and Jeff says he will pay that night. Tony Pirelli (Chico Marx) sends a telegram to lawyer J. Cheever Loophole (Groucho Marx). Julie reads a news article that Mrs. Dukesbury (Margaret Dumont) has disinherited Jeff. Julie and Jeff plan to marry and sing "Two Blind Loves." Tony greets Loophole but won't let him on the train in the rain.
On the train Tony plays piano for the women, and Loophole sings "Lydia the Tattooed Lady." Carter sends Goliath (Nat Pendleton), who knocks out Jeff and takes the money. Loophole, Tony, and Punchy (Harpo Marx) find Jeff and aim to get the money back. Loophole and Tony question Goliath but are intimidated. Punchy found a cigar. So Loophole and Tony question the midget (Jerry Maren), but Tony spoils it by providing cigars. Peerless Pauline (Eve Arden) performs walking upside down, and Loophole tries to get information about Carter. Pauline kisses Loophole and takes her wallet back. She gets Loophole to walk on the ceiling with her. Jeff suggests that Julie take another job. Tony tells Loophole to get Mrs. Dukesbury to give Jeff the money. Punchy and black kids play boogie and "Blue Moon."
Mrs. Dukesbury invites only "the 400." Loophole arrives as Mr. Dukesbury and asks her for $10,000 to entertain her party. Jeff kisses Julie and sings again. Tony and Punchy search Goliath's room while he sleeps. Punchy cuts the pillow, blanket, and mattress. Loophole calls Jeff to play the circus on Mrs. Dukesbury's lawn. Loophole calls a captain to detain her orchestra leader Jardinet. At the banquet Loophole counts the 400 and says no second helpings. As the circus arrives, Loophole tells Mrs. Dukesbury he loves her. Carter has men try to stop the show; but Jeff, Tony, and Punchy stop them. Punchy throws an ostrich egg at Goliath. Jardinet (Fritz Feld) arrives and complains of animals. Loophole tells Tony to send off Jardinet. Curtains reveal the circus, and Mrs. Dukesbury faints. Jardinet conducts Wagner as the bandstand floats away. Mrs. Dukesbury cheers Jeff. Carter releases the gorilla, who chases Carter. Punchy distracts them. Tony shoots Mrs. Dukesbury from a cannon and tries to rescue her from the trapeze. All are saved, and the gorilla counts the money.
Groucho wonders if he can accomplish his purpose without offending the Hayes Commission, and the Marx brothers manage to provide their unique blend of wit, puns, music, satire, and slapstick.