Sir John Falstaff has rolled into the town of Windsor, England, with his posse of "cony-catching rascals" and he's at it again. (What's that? You haven't met Falstaff, yet? No problem. Allow us to introduce you. He's the "fat," jolly knight who spends 99% of his time eating, boozing, thieving, "whoring," and causing mayhem in Henry IV Part 1 and Henry IV Part 2.)
When we catch up with Falstaff in this play, he's completely broke, which has put quite a damper on his rock-star lifestyle. But Falstaff's got a plan. He'll put the moves on a couple of rich housewives named Mistress Ford and Mistress Page (i.e., the "merry wives" of Windsor). The housewives have total access to their husbands' money so Falstaff thinks he can solve all his financial troubles by luring them into bed with a couple of super-steamy (okay, super-cheesy) love notes.
Since Falstaff's such a busy guy, the love notes are identical except that one says "Dear Mistress Page" and the other says "Dear Mistress Ford." There's just one hitch. Mistress Page and Mistress Ford are BFFs, which means they tell each other EVERYTHING. When they find out that Falstaff has sent them identical letters, they're seriously offended that (1) Falstaff just assumes they'll cheat on their husbands and (2) Falstaff has sent them the same, ridiculous letter.
Our "merry wives" hatch a plot to teach Falstaff a lesson he won't forget. They pretend to like him and invite him over for a secret rendezvous with Mistress Ford while her husband is away. To complicate matters, Falstaff's frenemies, Pistol and Nim, have decided to rat out Falstaff to the women's husbands. Master Page trusts his wife and couldn't care less about Falstaff but, Master Ford is crazy jealous.
Ford assumes his wife will get down and dirty with Falstaff since all women are liars and cheats, so he disguises himself as a guy named "Brooke" and becomes Falstaff's newest drinking buddy. When "Brooke" offers Falstaff a boatload of money to help him seduce Mistress Ford, Falstaff takes it and tells "Brooke" that, actually, he's going to hook up with Mistress Ford when her husband's away from home.
Meanwhile, over in the B-plot, the Pages' teenage daughter Anne has three guys (Slender, Caius, and Fenton) falling all over themselves to marry her because she's (1) rich, (2) still a virgin, and (3) smokin' hot. (In that order.)
Back to the main plot. Soon enough, Falstaff shows up at Mistress Ford's house looking to score. When Master Ford comes home, the wives stash the "fat" knight in a basket of stinky laundry that hasn't been washed in months and then dump it—and him—into the Thames River. Punk'd!
It's so much fun that our merry wives lure Falstaff back to the Ford house a second time. When Master Ford shows up (again), the wives disguise Falstaff as a local "witch" named "the old woman of Brentford." Master Ford goes nuts and beats "her" black and blue. The women think this is absolutely hilarious and let their husbands in on their little joke, which makes Master Ford all apologetic.
Now the couples get together to hatch a new plot. The plan is to get Falstaff to wear a silly costume ("Herne the Hunter") and have him meet them at the old haunted oak tree. Then, a bunch of townspeople and local kids dressed up as creepy little fairies will jump out of the bushes and terrorize him.
Got all that? Okay, good. This is where Shakespeare ties in his subplot to the main action of the play. Master Page tells Slender to elope with Anne on the same night, and tell him that's he'll be the "fairy" dressed in white. Mistress Page tells Caius the same thing, except that Anne will be the "fairy" dressed in green. Way to pimp out your daughter, guys.
Everything seems to be going as planned. Falstaff is terrified, and Caius and Slender each run off with green and white fairies. Falstaff tries to run away from the fairies but, before he can get away, Ashton Kutcher runs out and shoves a video camera in Falstaff's face.
Just kidding. The Fords and the Pages run out and confront him. Falstaff knows he's been had so he admits that he's been made into an "ass" and all is forgiven.
Just as we're wondering what happened to Caius and Slender, they both show up with two boys in green and white fairy costumes, griping about almost getting accidentally hitched to a couple of kids. Then Anne and Fenton show up and are all "Fooled you! We're married and there's nothing you can do about it." The Pages have a good-natured laugh about the whole thing and invite everyone back to their house for a wedding feast.