Jerry informs Lucy that he's taking a vacation alone in Florida; instead, he holes up with his buddies and plays poker for a week (while sitting under a sun lamp so he'll have an appropriate tan).
Lucy concludes that Jerry was never in Florida just as Jerry discovers that Lucy was spending her time with Armand Duvalle (Alex D'Arcy), a handsome voice teacher.
Both Jerry and Lucy believe the other was unfaithful, so they agree to a trial divorce, with a bitter battle fought over custody of Mr. Smith, the dog (Lucy gets the dog, but Jerry has visitation rights).
Determined to make Jerry jealous, Lucy continues keeping company with Armand while also dating Daniel Leeson (Ralph Bellamy), a wealthy oil man from Oklahoma. Convinced that turnabout is fair play, Jerry starts going out with Dixie Belle Lee (Joyce Compton), a brassy nightclub singer, as well as socialite Barbara Vance (Molly Lamont).
However, Lucy has belatedly decided that she wants Jerry back, and she hatches a plan to win him back by making a spectacle of herself at a party.
The Awful Truth was based on a play which had been filmed twice before, but McCarey gave his superb comic cast free reign to improvise and add new business, and the results were splendid; you haven't lived until you've heard Irene Dunne attempt to sing Home on the Range.