Sebastian is Viola’s twin brother. After the shipwreck, he was rescued by Antonio, and spent three months in his company.
Deciding that he cannot continue moping over his sister’s death, he sets forth for Orsino’s court, but on arriving in Illyria he discovers that Antonio has followed him. He proceeds to have a very confusing day, where his enjoyment of the usual touristy activities of sightseeing are continually interrupted by a series of mad people who claim to know him, including a pair of insulting ones with whom he almost ends up in a fight. His bafflement and belief that all Illyrians are insane do not stop him from following the beautiful woman who breaks up the fight, however. He is not entirely unconvinced that he’s dreaming, but can find no good reason not to follow this woman and the priest she drags in, and so goes along with her plans of secret marriage. Meeting his two opponents again, he shows them no mercy, breaks their heads, and rushes to apologize to his wife—only to discover that his sister is alive and that Olivia originally fell in love with her, not him. he confusion is quickly cleared up, and all is well. Sebastian seems an uncomplicated fellow, as quick to anger as to calming down, loyal and generally well-disposed.