Most of the events of the play take place in the city of Illyria (Italy), where Duke Arsino resides, who has been in love for quite some time with a noble woman named Olivia. But she did not return his love for love, and did not allow any other fiancé to approach her since her brother's death. She rejects the Duke's request on the pretext that she is determined to devote her life for seven years to mourning her dead brother.
There was a twin sister of a woman from the people of Mslini called Viola, and her brother was called Sebastian, and it was thought that he drowned in the sea during a storm, while his sister Viola survived with the help of the ship's captain. When Viola heard about the Duke, she thought of applying to serve him as a boy, so she wore clothes similar to her brother's clothes, and one of his followers presented her to the Duke. The Duke leaned towards her, told her of his love for Olivia, and used her to plead his case before her.