Shipwrecked twins Viola and Sebastian each believe the other has perished. Disguising herself as a young man named “Cesario,” Viola enters into the service of Duke Orsino. As Cesario, she delivers messages of love from Orsino to Olivia—but Olivia falls for Cesario (Viola), not realizing her true identity. Meanwhile, Sebastian arrives, mistaken for Cesario, creating romantic chaos.
 
In a comic subplot, Sir Toby Belch, Maria, and Sir Andrew Aguecheek prank the fussy steward Malvolio by forging a letter that leads him to behave absurdly, thinking Olivia loves him.
 
In the end, identities are revealed: Viola and Sebastian reunite, Orsino proposes to Viola, and Olivia realizes her love for Sebastian. Malvolio’s humiliation is exposed, and order is restored, with romantic reconciliations all around.