Setting: Windsor, England, during the reign of Henry IV (1399-1413)
At the Garter Inn, after a run-in with Dr. Caius, Falstaff discovers that he doesn’t have enough money to pay for his dinner. To support the expanding kingdom that is his paunch, he settles on seducing Alice Ford and Meg Page, wives of two of Windsor’s wealthiest burghers. His thieving sidekicks, Bardolph and Pistol, refuse to deliver love letters to the women, so Falstaff dismisses them and has a page do it instead.
Alice and Meg compare the letters as they relax in the garden by Ford’s house, noticing that the notes are identical. They decide to play a little joke on the fat knight. As the women leave, Dr. Caius, Bardolph, Pistol and Fenton arrive with Ford, who is getting an earful about what a trickster and scoundrel Falstaff is. Pistol tells Ford about the fat knight’s plan to dishonor Alice and empty the burgher’s coffers, so Ford decides to go to the inn in disguise and catch Falstaff. Meanwhile, the ladies enlist Mistress Quickly to lure Falstaff into their own trap. Whenever they can steal a moment, Fenton and Nannetta, the Fords’ daughter, enjoy a clandestine kiss.
Back at the inn, Quickly brings Falstaff a response from the two ladies. Both return his affections, but only Alice can meet him, any afternoon between two and three, while her husband is out. Bardolph informs Falstaff that a “Master Fountain” (Ford in disguise) wishes to make the knight’s acquaintance and give him a good bottle of Cyprian wine. “Fountain” tells Falstaff that he has fallen in love with Alice and promises the knight a sack of gold for seducing her, explaining that if she slips once, she’ll most likely slip again. Falstaff happily accepts the challenge. Indeed, he admits, he is well along with his own plan to cuckold Alice’s husband.
Quickly returns to Ford’s house to tell Meg and Alice that Falstaff has taken the bait. Nannetta complains that her father plans to marry her off to old Dr. Caius. Servants enter with a basket of dirty linen, while the ladies prepare their trap by setting up a screen between the basket and the fireplace. Falstaff arrives, but the rendezvous is interrupted when he and Alice her Ford approaching. Falstaff hides behind the screen while Ford, Dr. Caius, Bardolph and Pistol search for him. Believing that Falstaff is hiding behind the screen, Ford throws it aside only to discover his daughter and Fenton. Infuriated, he and the rest of the men rush off. Alice summons the servants to deal with the laundry. They struggle with the basket but finally manage to dump it, and Falstaff, into the Thames River.
Outside the inn, Falstaff drowns his sorrows in wine. Quickly arrives and convinces him that Alice wants to meet him at midnight in Windsor Park, but he has to come dressed as a fairy-tale character, the Black Huntsman. Hidden behind a house, the husbands, wives, and others overhear the conversation, and Quickly arrives just in time to hear Ford plotting the doctor’s marriage to Nannetta.
At the park that night, the wives make some costume changes to foil Ford’s marriage plans for Nannetta. Midnight approaches, and Falstaff enters wearing antlers on his head and wrapped in a huge black cloak. His encounter with Alice is interrupted, this time by the assembled company disguised as spirits. They torment Falstaff and force him to repent, but recognizing Bardolph in the midst of the revelry, Falstaff realizes that he has been duped yet again. Ford announces that, to end their festivities, they shall celebrate the marriage of the Fairy Queen. Dr. Caius steps forward and takes the hand of the Queen, believing her to be Nannetta. Another masked couple also approaches to take their vows. Only afterward is it revealed that the Queen was Bardolph and that Fenton and Nannetta were the masked couple. Ford accepts the situation, and the opera closes with a mighty fugue praising the hilarity of life.