Cesario retreats into the house, but Sir Andrew pursues him. Once Sir Andrew has left to await Cesario, Sir Toby reveals that he will not deliver the letter to Cesario, but instead goes and tells ‘him’ about Sir Andrew’s challenge in person. Malvolio leaves, and Sir Andrew appears with his letter of challenge drafted for Cesario, challenging ‘him’ to a duel over Olivia. She leaves to welcome Cesario back, and Sir Toby, Maria, and Fabian confront Malvolio, pretending to think him mad. Olivia speaks with Malvolio, and is shocked by his attire and his perpetual smiling. When he’s gone, Maria arrives to tell Sir Toby and Fabian that Malvolio has acted upon the advice in the forged letter, and is cross-gartered and wearing yellow stockings.

Sir Toby and Fabian persuade Sir Andrew to write a letter challenging Cesario to a duel: they say that Olivia is bound to be impressed by his valour.

Sir Andrew Aguecheek, who walked in on them, complains to Sir Toby and Fabian that Olivia, who spurns his advances, was bestowing her affection upon a mere servant. Viola, as Cesario, has another audience with Olivia, during which Olivia confesses her love for ‘him’. When Malvolio is gone, Sir Toby and the others laugh at Malvolio’s gullibility. The letter also suggests that Malvolio smile in Olivia’s presence, so that she might discreetly know he returns her affections. Sir Andrew, convinced Olivia will never agree to see him, is intent on giving up the chase, but Sir Toby persuades him to stay a little longer, convincing him that he has a chance with the countess. Sir Toby’s friend, Sir Andrew Aguecheek, arrives Sir Toby is trying to put in a good word for his friend, who is trying to woo Olivia (unsuccessfully). Olivia’s uncle, a drunken aristocrat named Sir Toby Belch, is chastised by Olivia’s gentlewoman and chambermaid, Maria, for coming home late, drunk. Viola, keen to establish herself in this new place, decides that she will serve Orsino, disguising herself as a male youth named Cesario. Meanwhile, a lady named Viola is shipwrecked on the coast of Illyria, and fears her twin brother, Sebastian, with whom she was travelling, may have died during the wreck. Olivia has vowed to shut herself away from society for seven years as a result of these deaths.

The play opens with the Duke of Illyria, Orsino, pining away with love for Olivia, a countess whose father died a year ago and whose brother has recently died.

William shakespeare 12th night