J.B. Ball [Edward Arnold], the third richest banker in America, shares a tense breakfast with his son John Jr. [Ray Milland], a confrontation that ends with John leaving to prove he can make his own way. Ball’s fury erupts again when he learns his wife Jenny Ball [Mary Nash] bought a sable fur coat worth $58,000, and he insists it must be returned. After discovering the coat in her closet, he grabs it, Jenny wrestles it away, and the chase drives them to the roof of their New York City penthouse, where Ball hurls the sable coat over the edge.
It lands on Mary Smith [Jean Arthur] as she rides to work on a double-decker bus. When she tries to return it, Ball tells her to keep it, conveniently withholding just how valuable it is. He also buys her a lavish new hat to replace the one lost in the incident, which leads Van Buren [Franklin Pangborn], the magazine’s shopkeeper, to mistake Mary for Ball’s mistress. The rumor mill explodes, and when Mary shows up for work, her straitlaced boss suspects impropriety and fires her to protect the reputation of the Boy’s Constant Companion, the magazine he publishes.
Left nearly penniless, Mary begins receiving offers from people eager to capitalize on her notoriety. Hotel Louis owner Mr. Louis Louis [Luis Alberni] installs her in a luxury suite in the Hotel Louis, hoping this will deter Ball from foreclosing on the establishment. While Mary is at an automat enjoying a meal, she meets John Jr. [Ray Milland], who is working there undercover. He’s fired after giving Mary free food and starting a friendly food fight, yet Mary learns he has nowhere to stay and invites him to share her suite as he searches for work. The pair quickly fall in love, even as Ball’s world becomes unsettled by the sudden visibility Mary has gained.
Meanwhile, Ball’s wife returns from Florida and he moves into the Hotel Louis, with gossip columns buzzing about a supposed affair. The hotel’s glamorous atmosphere attracts the elite, and luxury firms begin showering Mary with gifts—jewelry, clothes, and even a sixteen-cylinder car—while her rumored link to Ball continues to ripple through society.
The tension thickens when stockbroker E.J. Hulgar [Andrew Tombes] asks Mary for inside information about steel from Ball. Confused, Mary turns to John Jr., who jokes that the steel will go down, and she relays his remark to Hulgar. That misinterpretation triggers a sell-off that sends the market into a tailspin as Ball starts buying up shares, pushing his firm toward the brink of disaster.
Jenny returns from Florida, and as Mary, John, and J.B. piece together what’s really going on, John proposes a clever fix. Mary tells Hulgar that J.B. has cornered the steel market, and the plan pays off as prices surge, saving the financier. The grateful J.B. offers John Jr. a position, and John, in turn, asks Mary to become his wife, sealing a conclusion that reconciles ambition, romance, and a high-stakes financial riddle with a hopeful future.
