what happens when antonio enters and sir andrew and viola are drawn on one another?

Antonio enters. He sees Cesario and mistakes him for his beloved Sebastian, and tells Sir Andrew that he, Antonio, will fight Sir Andrew in Sebastian’s place. Several Illyrian officers burst onto the scene. They have recognized Antonio—a wanted man in Illyria—and arrest him. Antonio, realizing that he will need to pay a bail bond in order to free himself, asks Cesario, whom he still believes is Sebastian, to return his purse (which Antonio gives to Sebastian in Act III, scene iii). Viola, however, has no idea who Antonio is. Antonio thinks that Sebastian is betraying him by pretending not to know him, and he is heartbroken. Deeply shocked and hurt, he rebukes Sebastian. The officers, thinking Antonio is insane, take him away. Viola is left with a sudden feeling of hope: Antonio’s mention of someone named “Sebastian” gives her some hope that her own brother—whom she has thought dead—is in fact alive and nearby. Viola runs off to look for him, leaving Sir Andrew and Sir Toby very confused.