Disclaimer: the origional 'Twelfth Night' was written by Shakespeare. What you read here is by no means all of what happens in the play.
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Alas! A woman is shipwrecked onto Illyria, and believes her twin brother is dead.
Behold! The fair countess Olivia, whom the Duke loves, is mourning her dead brother.
Cesario, the shipwrecked woman in the guise of a man, gets a job in the Duke Orsino's court.
Deserted gardens are much to (Olivia's steward) Malvolio's liking, for there he can pump up his ego as much as he wants.
Except that this time Maria, Olivia's maid, and Toby, Olivia's cousin, are listening. They decide on a plan to drive Malvolio crazy.
Fabian talks to Toby and Sir Andrew, a knight who is trying to woo the countess, and agrees to be part of the trick on Malvolio.
Going to deliver Orsino's love thoughts to Olivia, Cesario unwittingly makes Olivia fall in love with him/her.
Hearing Malvolio approaching, Maria leaves a letter on the ground that Malvolio picks up and reads.
In the letter, there's reason to believe that Olivia is confessing her love for Malvolio, and the Steward mistakenly believes the letter.
Just then, we see that the twin brother, Sebastian, was saved by a sea captain called Antonio, but believes his sister is drowned. He sets out for Orsino's court.
Keeping with every point in the letter, Malvolio shows himself to Olivia, revealing his yellow stockings, cross-gartered, and smiling. Olivia thinks he's mad (crazy), and sends for Toby. Toby tossed Malvolio into a darkhouse, chained and blindfolded.
Looking for entertainment, Sebastian wanders around Illyria.
Maria gets the Fool to pretend to be a priest and torment Malvolio.
Nearly everyone who sees Sebastian thinks he's Cesario, and Sebastian is very confused.
Orsino takes Cesario and heads to Olivia's.
Pouncing on the new arrival, Olivia also thinks that Sebastian is Cesario, and is overjoyed when he says that he will marry her.
Quite suddenly, Orsino arrives at Olivia's house to try and win her love.
Revealing that she had married Cesario, Olivia calls forth the holy father to prove it.
Saddened by the loss of Olivia and angered that his own man, Cesario, married her behind his back, Orsino spurns Cesario.
Then Sebastian enters the scene, surprising everyone who thought that there was only one Cesario.
"Utopia I would gladly give up, to have my sister Viola alive." Sebastian says.
"Viola! I am Viola!" Cesario cries, revealing her true self to everyone present.
What? Cesario is really a woman? Orsino fall instantly in love with her.
'Xylophones and wild horses could not tear me away from you!' Orsino wants to shout, but instead he says "When in other habits you are seen, Orsino's mistress, and his fancy's queen."
Young though they are, the twins Viola and Sebastian have both snagged courtier spouses.
Zeus shines down upon the world, as the fool sings a song and ends the play.