Antonio gives Sebastian his purse upon landing at Illyria and tells him to buy whatever he pleases. When Antonio sees Viola/Cesario, he assumes that this young man is Sebastian and that Sebastian still has Antonio's purse.
After saving Viola from her attacker, Antonio is confronted by an old enemy, who demands that Antonio answer for an offense he had committed years before. At this point in the play, Antonio asks Viola, believing Viola to be Sebastian, for his purse back so that he can pay off his enemy. Viola, however, refuses to give him a purse because she does not know who he is and does not have his purse. Antonio is dragged off to prison, believing his friend Sebastian has betrayed him.