Iago continues to torment Othello with vivid descriptions of Desdemona’s alleged sexual activity. Othello falls into an epileptic seizure. Iago next places Othello where he can see (but not hear) a conversation between Cassio and Iago about Bianca, telling Othello that the bawdy talk is about Cassio and Desdemona. Othello’s fury grows.
Lodovico arrives from Venice with orders from the duke and senators that Othello return to Venice and that Cassio be appointed in his place. Othello strikes Desdemona in Lodovico’s presence, then rudely dismisses her, leaving in a jealous rage. Lodovico expresses his astonishment at the change in Othello.