Based on the musical play by George F. Kaufman and Morrie Ryskind, the four Marx brothers have fun and games spoofing high society at the Long Island estate of Mrs. Rittenhouse.
The musical number "Hooray for Captain Spaulding" welcomes back from Africa the wise-cracking Groucho, who repeatedly sings in a bass voice that he must be going. Spaulding makes fun of the swanky mansion and tries to sell Mrs. Rittenhouse (Margaret Dumont) an insurance policy. Musician Emanuel Ravelli (Chico Marx) discusses his fees with Spaulding, charging more for rehearsing and not playing than he does for playing. The Professor (Harpo) acts out fantasies by removing his cape to reveal his underwear, scattering people by shooting guns, and chasing after a pretty woman. The complicated plot involves stealing and replacing a donated painting of great value, as a poor artist tries to gain money by getting his copy recognized so he can marry Mrs. Rittenhouse's daughter.
Spaulding tries to woo Mrs. Rittenhouse and says he had her "on the five-yardline" when Mrs. Whitehead intervenes. So he praises their "four beautiful eyes," charm, and money, suggesting they all get married. Speaking aside to the audience, he parodies Eugene O'Neill's strange interludes as he expresses his doubts. Mrs. Rittenhouse points out it would be bigamy, but Spaulding merely notes that it's "big of me too." He wants a bigger marriage; he may even add another woman or two on the honeymoon, but no men; in fact he may not even go himself. Then he leaves the older women to sow some wild oats with the chorus girls in swimsuits.
The art expert Chandler is apparently a fake and offers to bribe the eager Professor. Spaulding suggests solving economic problems with an "eight-cent nickel" so that it will go farther. The plays on words and gestures result in many ludicrous and absurd insights. Because their antics are perceived as harmless, Groucho, Chico, and Harpo are allowed to get away with what is normally socially unacceptable. Harpo tries to get several people to hold his leg up; when asked to choose his seat, he sits in a woman's lap; and in the bridge game he deals himself a pile of aces. Chico plays the piano but can't think of the finish; Groucho says he can't think of anything else. Spaulding's secretary (Zeppo) plays straight man for Groucho's parody of writing a business letter. When a police detective shows up, Spaulding and Ravelli ineptly try to solve the robbery case. Insulted, Spaulding wishes to be back in the jungle where men are monkeys. Caught stealing the silverware, the Professor finally puts everyone out of their misery with a spray-can of ether, positioning himself next to the blonde he's been chasing before he knocks himself out.
These human animals are full of cracks.