‘Twelfth Night’ opens on Duke Orsino listening to music, pining away for the love of Lady Olivia. He cannot have her because she is in mourning for her dead brother and refuses to entertain any proposals of marriage. Meanwhile, off the coast, a storm has caused a terrible shipwreck, resulting in a young woman named Viola being swept ashore. Finding herself alone in a strange land, she assumes that her twin brother – Sebastian – has been drowned in the wreck, and tries to figure out what she should do in order to survive in this new, unfamiliar place. A friendly sea captain tells her about Orsino’s courtship of Olivia, and Viola says that she wishes she could go to work in Olivia’s home. But since Lady Olivia refuses to talk with any strangers, Viola decides that she cannot look for work with her, instead deciding to disguise herself as a man, taking on the name of Cesario, and going to work in the household of Duke Orsino. Viola – disguised as Cesario – quickly becomes a favourite of Orsino, who makes Cesario his page. Viola finds herself falling in love with Orsino, but when Orsino sends Cesario to deliver a love messages to the disdainful Olivia, Olivia herself falls for the beautiful young Cesario, believing her to be a man. Viola loves Orsino, Orsino loves Olivia, and Olivia loves Cesario; and everyone is miserable.
Meanwhile, Olivia’s rowdy drunkard of an uncle, Sir Toby, is trying to assist his idiot of a friend, Sir Andrew Aguecheek, with his attempts to court Olivia. They are helped in their endeavour by Olivia’s gentlewoman, Maria, and Feste, the fool of the house. However, Malvolio – Olivia’s steward – seeks to quash their fun at every turn, leading to Maria engineering a practical joke to make Malvolio think that Olivia is in love with him. She forges a letter, supposedly from Olivia, addressed to ‘her beloved’ (whose name is signified by the letters M.O.A.I.), telling him that if he wants to earn her favour he should dress in cross gartered yellow stockings, smile constantly, and refuse to explain himself to anyone. Malvolio finds the letter, assumes that it is addressed to him, and – filled with dreams of marrying Olivia and becoming noble himself – happily follows its commands. He behaves so strangely that Olivia comes to think that he is mad.
INTERVAL
On top of all this, Sebastian – who is still alive after all but believes his sister Viola to be dead – arrives in Illyria along with his friend and protector, Antonio. Antonio has cared for Sebastian since the shipwreck and is attached to the young man, so much so that he follows him to Orsino’s domain, in spite of the fact that he and Orsino are old enemies. Sir Andrew, observing Olivia’s attraction to Cesario (Viola in disguise), challenges Cesario to a duel. Sir Toby, who sees the prospective duel as entertaining fun, eggs Sir Andrew on. However, when Sebastian—who looks just like the disguised Viola—appears on the scene, Sir Andrew and Sir Toby end up coming to blows with Sebastian, thinking that he is Cesario. Olivia enters amid the confusion. Encountering Sebastian and thinking that he is Cesario, she asks him to marry her. He is baffled, since he has never seen her before, though sees that she is wealthy and beautiful, and is therefore more than willing to go along with her. Meanwhile, Antonio has been arrested by Orsino’s officers and now begs Cesario for help, mistaking him for Sebastian. Viola denies knowing Antonio, and Antonio is dragged off, crying out that Sebastian has betrayed him. Suddenly, Viola has newfound hope that her brother may be alive.
Malvolio’s supposed madness has given Maria, Toby, and Feste cause to lock him in a mad house for treatment, tormenting him at will. Feste dresses up as ‘Sir Topas’, a priest, and pretends to examine Malvolio, declaring him insane in spite of his protests. However, Sir Toby begins to think better of the joke, and they allow Malvolio to send a letter to Olivia, in which he asks to be released.
Eventually, Viola (still disguised as Cesario) and Orsino make their way to Olivia’s house, where Olivia welcomes Cesario as her new husband, thinking him to be Sebastian, whom she has just married. Orsino is furious, but then Sebastian himself appears and all is revealed. The siblings are joyfully reunited, and Orsino realizes that he loves Viola, now that he knows she is a woman, and asks her to marry him. We discover that Sir Toby and Maria have also been married privately. Finally, someone remembers Malvolio and lets him out of the dark room. The trick is revealed in full, and the embittered Malvolio storms off, leaving the happy couples to their celebration.
(Adapted from http://www.sparknotes.com/shakespeare/twelfthnight/, 05/02/2018)