Twelfth Night is the last night of the Christmas season, when the normally rigid households of Shakespeare’s day permitted a degree of topsy-turvey. Playing with this theme of confusion, Shakespeare’s Twelfth Night; or, What You Will begins with a shipwreck on the coast of Illyria. Washed up separately, the twins Sebastian and Viola each believe the other to be drowned. Viola disguises herself as a young man called Cesario and enters the service of Duke Orsino. Cesario quickly becomes a favourite and is sent to woo Countess Olivia on Orsino’s behalf. Olivia, who has vowed to mourn her brother for seven years, falls in love with Cesario. Viola secretly falls in love with Orsino.
Sir Andrew Aguecheek also attempts to woo Olivia, though he stands little chance and is merely being strung along by Olivia’s drunkard uncle, Sir Toby Belch, who wants to keep Sir Andrew at the house to fund his revels. Olivia’s puritanical steward, Malvolio, warns Belch, Aguecheek and Maria (Olivia’s gentlewoman) about their drunk and rowdy behaviour, so they trick him into believing Olivia is in love with him and wants him to dress in yellow, cross-gartered stockings to prove he loves her too. When he does, and quotes from a love-letter forged in her hand, she thinks him insane and he is locked up.
Sir Toby convinces Andrew that Olivia’s shows of affection for Cesario are in fact attempts to spur him into action, and convinces him to challenge the interloper to a duel. Meanwhile, the sea captain Antonio has rescued and befriended Sebastian. Antonio comes upon the duel, mistakes Cesario for Sebastian, steps in and is captured. He is heartbroken when Cesario denies knowing him. In turn, Sebastian is mistaken for Cesario by Olivia and quickly agrees to marry her. After further confusion, the twins meet in front of the other characters. All is revealed and Olivia marries Sebastian, Viola marries Orsino, and Sir Toby marries Maria, while Malvolio leaves vowing revenge.
Click here for a short PDF summary of the sources relating to Twelfth Night from 'Discovering Literature: Shakespeare'.