- In front of Olivia's house, Fabian and Feste argue about a letter that Feste won't show Fabian.
- Duke Orsino, "Cesario," Curio, and some Lords show up looking for Olivia. Feste makes some clever comments and jokes and Orsino gives him some money for being so entertaining. Feste then convinces Orsino to give him some more gold.
- Orsino tells Feste to fetch Olivia and the clown runs off.
- Just then, Antonio and the cops happen to walk by and Orsino recognizes Antonio as a sea captain that once caused him and his fleet of ships a lot of grief.
- "Cesario" says Antonio's the guy who stood up for "him" when Aguecheek and Toby tried to beat "him" up, but Orsino doesn't care. He can't believe Antonio has the nerve to show his face in Illyria when he's a wanted man.
- Antonio says he's not a pirate, even though he's Orsino's enemy. Then he points at "Cesario" (who he thinks is Sebastian) and whines about the way Sebastian treated him.
- Antonio says that, even though he saved Sebastian's life, has been a loving and devoted companion, and has followed Sebastian to Illyria, where he saved his life again, Sebastian has betrayed by pretending not to know him and by refusing to give him back the money he needs to buy his way out of jail.
- "Cesario" is dumbfounded.
- Orsino says Antonio's story isn't possible because "Cesario" has been in Illyria for three months, not one day, so Antonio must be lying.
- Olivia and her attendants come outside and Duke Orsino tries to lay some smooth moves on her, but Olivia's not having any of it. She yells at "Cesario" for neglecting her so soon after their marriage. (Olivia has married Sebastian off-stage but she thinks she married "Cesario.")
- Orsino tells "Cesario" to come with him, but Olivia says, "Husband, stay." Husband? That gets everyone's attention.
- When Orsino hears that his trusty page "Cesario" married the woman of his dreams, he's furious. "Cesario" tries to protest, which angers Olivia.
- Then the priest enters and says that yep, he just married Olivia to "Cesario." (The priest thinks "Cesario" is Sebastian, too.)
- Orsino calls "Cesario" a conniving little liar and says he never wants to see "him" again.
- "Cesario" tries to protest again, but it's tough to get anyone to believe you when it's your word against a priest's.
- To make matters worse, Aguecheek runs out and says that "Cesario" just beat him up. He beat up Toby, too. (The audience knows that it was Sebastian, not "Cesario.")
- "Cesario" denies everything, but Toby runs out and corroborates Aguecheek's story. Both men are bleeding and, when Toby asks if anyone has seen the local doctor, Feste informs him that the doctor has been drunk since eight o'clock in the morning – he's not going to come.
- This infuriates Toby, who announces that he hates all drunks.
- Olivia tells Toby get out and says that Sir Andrew needs to get to bed and be looked after.
- Andrew says he'll leave with Toby since they're in this together, but Toby insults him, calling him a coward and an idiot.
- Finally, Sebastian saunters in and says he's sorry to Olivia for beating up her uncle Toby.
- Everyone is shocked and amazed that there seems to be two "Cesario's" standing on stage.
- Sebastian recognizes Antonio (who is still in handcuffs) and is overjoyed to see his bosom friend. Antonio is amazed. He asks Sebastian if he's split himself in two.
- Sebastian notices "Cesario" standing nearby and says he can't believe there's a guy out there who looks just like him. He wants to know who "Cesario's" parents are and where "Cesario" comes from.
- Instead of coming out and saying, "Hey, I'm Viola, your sister," Viola is cryptic and says her father's name is Sebastian. That's her brother's name too, but he's drowned and dead.
- Sebastian still hasn't figured it out. He says that if "Cesario" were a woman, he would look just like his long lost sister Viola, who is dead.
- Viola then says her father had a mole on his face and Sebastian says gee, my dad had a mole on his face, too.
- When Viola announces that her dad died on her thirteenth birthday, Sebastian finally understands that "Cesario" is in fact his sister, Viola.
- Finally, Viola says what she should have said long before—"I'm Viola dressed as a boy. I'd put my girl clothes back on now but I left them with the sea captain who fished me out of the ocean so I'll have to stay in these clothes."
- Sebastian looks at Olivia and says it's lucky for her that she married him instead of "Cesario." Otherwise, she would have mistakenly married a woman when she thought she was marrying a man. As it is, she's now married to both a man (Sebastian) and a woman (her new sister-in-law, Viola).
- Orsino tells Olivia not to worry about this turn of events, because Sebastian comes from noble blood, which means Olivia hasn't just married a servant boy ("Cesario") after all. And, Orsino says, he stands to gain here, too.
- Orsino turns to Viola, and calls her "boy" (even though he knows she's a girl) and reminds Viola of all the times "Cesario" told him "he" loved him.
- Viola confirms that yes, she is totally in love with Orsino.
- Orsino grabs her hand and says he wants to see her in her "woman's weeds" (her dress).
- Viola says she can't do it because the sea captain's got her clothes and Malvolio is holding the sea captain prisoner.
- Olivia says she'll take care of Malvolio. She calls for him and Feste gives her the letter Malvolio wrote while imprisoned in the dark room.
- Feste says Malvolio's possessed by the devil, but, when he reads the letter aloud to Olivia, Olivia knows something's up.
- Orsino turns to Viola and says she doesn't have to be his servant anymore—lucky girl, she gets to be his wife now.
- Fabian trots out Malvolio, who says that he did everything in Olivia's letter (smiling, wearing wacky clothes, arguing with everyone) so she shouldn't have locked him in prison for doing what she asked.
- Olivia tells Malvolio that she didn't write the letter he's just shown her. That's Maria's handwriting.
- She tells Malvolio that when they figure out who's been pranking him, he can dole out the justice to make things right.
- Fabian jumps in and explains that he and Toby were just having a laugh. Toby convinced Maria to write the letter and married her as a reward for a job well done. Now, they should all just laugh at the outcome since Malvolio and the others all insulted each other equally.
- Malvolio doesn't see the humor in the situation. He runs off and swears he'll get revenge.
- Olivia says that poor Malvolio really got the raw end of the deal, but nobody really seems to care about Malvolio's feelings. Except that they need him to tell them where the Captain is so they can get Viola's clothes.
- Duke Orsino says that Viola will "be" Cesario until she changes out of her boy's clothes. But, when she puts her dress back on, she'll be his woman and they'll have the weddings.
- Everyone exits except the fool, who sings a silly—but kind of sad—song about growing up.
- It's about how things change as you get older and yet, life just keeps rolling on, with the rain coming every day.
- The last lines are happy though, as he say that the play is done and that the players will always strive to make their audience happy.