Preston Sturges adapted an uncredited play by Vera Caspary in this comedy about a banker who gives a sable coat to a stranger, who meets his useless son.
Banker J. B. Ball (Edward Arnold) objects to his son John Ball (Ray Milland) buying a foreign car. John says he will work for a living. J. B. sees a $58,000 bill for a sable coat and asks his wife (Mary Nash) about it. Finding several fur coats in her closet, he throws it off the roof, and it lands on Mary Smith (Jean Arthur) in a bus. Mary tries to return it, but J. B. gives it to her. He gives her a ride and tries to explain compound interest. J. B. buys Mary a sable hat. She writes for a boys magazine; but they question her about the coat and fire her. J. B. learns that his wife went to Florida. Louis (Luis Alberni) owes money for his hotel to J. B., who gives him a week. Mary owes $7 for a week's rent but gets a telegram to see Louis at his hotel. Louis shows Mary the imperial suite and gives it to her for $7 a week if she will boost the hotel.
Mary meets John working in the automat. He sneaks her a beef pie and is fired by the security guard and fights with him, causing mayhem while Mary eats. John leaves with Mary, who takes him to the Louis hotel. J. B. decides to stay at the Louis. Mary and John turn on the shower, and Louis brings her clothes to try on. Louis tells reporter Wallace Whistling (William Demarest) about J. B., who asks for a room with a bath and sees Mary. J. B. orders dinner for her, and Wallace calls in the story. Mary and John relax after dining, and he kisses her.
The article by Wallace makes the Louis fashionable. Mary gets calls offering her things. John and Mary look for jobs in the ads. A stock broker has Mary ask John about steel, and he says it is going down. J. B. says steel is going up; he sees steel is low and buys it. The broker calls Mary that she made $18,000. J. B. keeps buying steel while others object. John reads that Ball is tottering. Mrs. Ball comes in and forgives J. B. for the girl at the Louis. Mary buys two dogs and learns who J. B. is. John tells J. B. that he told Mary to tell someone steel would go down. Mary tries to see J. B., while he is trying to find her. Mary charges in with her dogs, and John suggests that Mary tell the broker that steel is going up; J. B. adds that he has it cornered. Mary calls the broker, gives the coat back to Mrs. Ball, and leaves. John goes after her, and police stop her. Steel is up, and J. B. says sell. John says sell more, and J. B. tells him to get to work. John tells Mary that they have jobs. J. B. throws the coat, and it lands on another woman.
This mad-cap comedy allows audiences to identify with someone suddenly given wealth who can now mingle with the upper class, while poking fun at the volatility of stocks.