Twelfth Night

Characters:

• Viola
• young woman of aristocratic birth
• twin sister of Sebastian
• disguises herself as "Cesario", page to Duke Orsino
• falls in love with Duke Orsino
• Orsino
• powerful nobleman in the country of Illyria
• lovesick for Lady Olivia
• Olivia
• wealthy, beautiful and noble Illyrian lady
• courted by Orsino and Sir Andrew Aguecheek
• insists that she is in mourning for her brother and will not marry for seven years
• Sebastian
• Viola's lost twin brother
• Malvolio
• straitlaced steward of Lady Olivia's household
• efficient but also very self-righteous
• tricked into believing Lady Olivia is in love with him
• Feste
• clown of Olivia's household
• Sir Toby
• Olivia's uncle who lives with her
• however Olivia does not approve of his rowdy behavior, practical jokes, heavy drinking, late-night carousing or friends
• Maria
• Olivia's clever, daring young waiting-gentlewoman
• Sir Andrew Aguecheek
• friend of Sir Toby's who attempts to court Olivia
• Antonio
• man who rescues Sebastian after his shipwreck

Plot summary:

• Orsino lies around pining for Lady Olivia who does not want to marry because she is mourning for her dead brother.
• Viola is swept ashore in a shipwreck and assumes that her twin brother Sebastian has drowned. 
• Viola disguises herself as a man under the name of Cesario and goes to work in Duke Orsino's household. She quickly becomes his favorite and made into his page, but she finds herself in love with Orsino. 
• Orsino sends her to deliver his love messages to Olivia but Olivia falls for Cesario/Viola. 
• Maria engineers a joke to make Malvolio think that Olivia is in love with him. She forges a letter, supposedly from Olivia, addressed to her "beloved" M.O.A.I, telling him that if he wants to earn her favor, he should dress in yellow stockings and crossed garters, act haughtily, 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, follows its commands. He behaves so strangely Olivia believes he is mad.
• Sebastian arrives in Illyria with his friend and protector, Antonio. Antonio follows Sebastian to Orsino's domain even though he and Orsino are old enemies.
• Sir Andrew, who wishes to court Olivia but notices her attraction to Cesario, challenges Cesario to a duel. Sir Toby eggs Sir Andrew on. However, when Sebastian, who looks just like the disguised Viola, appears, Sir Andrew and Sir Toby end up coming to blows with Sebastian.
• Olivia enters the scene and asks Sebastian to marry her, thinking he is Cesario. Although he has never seen her, she is beautiful and wealthy, and he is more than willing to go along with her.
• Antonio has been arrested by Orsino's officers and begs Cesario for help, mistaking him for Sebastian. Antonio is dragged off shouting Sebastian's name and Viola realizes her brother may be alive.
• Maria, Toby and the rest lock Malvolio in a small dark room as treatment for his madness. Feste dresses up as "Sir Topas", a priest, and pretends to examine Malvolio with the conclusion that he is definitely insane. However, they allow Malvolio to send a letter to Olivia in which he asks to be released.
• Viola as Cesario and Orsino make their way to Olivia's house, where Olivia welcomes Cesario as her new husband. Orsino is furious but then Sebastian appears on the scene. The siblings are reunited and Orsino realizes he loves Viola and asks her to marry him. Sir Toby and Maria also marry privately. Malvolio is released from the dark room and he storms off after realizing he has been tricked.