Viola, a young noblewoman, is shipwrecked and cast ashore in the country of Illyria. She believes her beloved identical twin brother Sebastian has drowned. Disguising herself as a young man (Cesario) she plans to find employment in the court of Duke Orsino.
Orsino believes himself in love with the aloof Countess Olivia, but she’s in deep mourning, which is also a useful excuse to rebuff Orsino’s unwanted advances. Olivia’s uncle Sir Toby Belch and his foolish companion, Sir Andrew Aguecheek, disturb the house with drunken escapades. Clever Maria, Olivia’s lady-in-waiting, attempts to keep some order, but can’t resist Sir Toby’s zest for life.
Orsino takes a shine to Cesario/Viola and sends him/her with a marriage proposal to Olivia. This is painful for Viola, since she’s fallen in love with Orsino herself, but of course as a “man” can’t show it.
Feste, a fool in Olivia’s household, casts a wry eye on events, but not everyone is a fan. Olivia’s pompous steward Malvolio takes pleasure in belittling Feste.
Cesario/Viola declares Orsino’s love to Olivia, but Olivia seems more interested in the messenger. Meanwhile lost identical twin brother Sebastian turns up alive and well in Illyria with faithful sea captain Antonio. Sebastian plans to travel to… Duke Orsino’s court! Malvolio gives Cesario/Viola a ring from Olivia. Viola realises the awful truth – Olivia has fallen in love with him/her!
Sir Toby, Sir Andrew, Feste, Maria and another servant Fabian are told off by Malvolio for drunken singing in the middle of the night. Annoyed, Maria concocts a plan to make Malvolio believe Olivia is in love with him. Back in Orsino’s court, Viola comes close to confessing her love for him.
Maria sets a trap for Malvolio with a forged letter from Olivia encouraging him to dress and behave outrageously.
Poor Cesario/Viola must deal with Feste’s jibes, Sir Toby’s jokes, Sir Andrew’s jealousy and finally Olivia’s lovesick advances.
Sir Toby and Fabian cook up another prank to make Cesario/Viola and the cowardly Sir Andrew fight each other.
Sebastian arrives in town eager to explore. Antonio lies low – as in Illyria he is an outlaw. Malvolio makes a fool of himself in front of Olivia, who believes he’s mad. She asks Sir Toby to take care of him.
The prank fight between Sir Andrew and Cesario/Viola backfires when Antonio turns up, mistakes Cesario/Viola for Sebastian and attacks Sir Andrew. Antonio is arrested, but when he appeals to Cesario/Viola, she has no idea who he is. Then Sebastian appears and is mistaken for Cesario by Sir Andrew. As Sir Toby starts to fight Sebastian, Olivia arrives to break it up. To Olivia’s delight this “Cesario” is much more amenable to her charms than the other one!
Sir Toby, Maria and Feste imprison Malvolio. Feste taunts him as a madman, while posing as the priest Sir Topas. Meanwhile the real Sir Topas is busy marrying Olivia and Sebastian.
Finally Viola and Sebastian are in the same place at the same time. Everyone is confused by the amazing likeness between them, but all becomes clear when sister and brother realise they are both still alive and Viola reveals her true female identity. Olivia is happy to find herself married to Sebastian and Orsino is now free to act on his own confused feelings and marry Viola. Sir Andrew and Sir Toby have been punished by Sebastian’s beating, but there is some compensation – Maria has married Sir Toby. Malvolio strikes a single sour note to demand his revenge, but the mood is joyful as Illyria celebrates the triumph of true love against all the odds.