Othello and Iago enter, discussing infidelity. Iago uses the conversation to further enrage Othello, then lets slip that Cassio has actually told him that he has slept with Desdemona. Othello grows frantic, almost incoherent, then falls into an epileptic fit.
Cassio enters while Othello is unconscious from his fit. Iago informs Cassio that this is Othello’s second fit in as many days, and though Cassio wants to help advises that it would be better if Cassio stayed away. He adds that he’d like to speak with Cassio once Othello is better.
Although Cassio shows real concern for Othello, Iago skillfully maintains exclusive control over his situation.
Othello’s fit ends after Cassio exits. Iago tells Othello that Cassio passed by during Othello’s fit and will soon return to speak with Iago. Iago says that he will get Cassio to talk about the details of his affair with Desdemona, and that Othello should hide and watch Cassio’s face during the conversation. Othello hides.
Alone, Iago explains to the audience that he will actually speak with Cassio about Bianca, who’s doting pursuit of Cassio never fails to make Cassio break out in laughter. This laughter will drive Othello mad.
At the play’s beginning, Othello was the center of the action, the military hero. Now, his honor gone, he skulks around the periphery, a kind of peeping tom. Cassio, by the way, is rather nasty to Bianca.
The plan works perfectly: as Cassio laughs and gestures, Othello grows angrier and angrier. Then Bianca herself enters, again accuses Cassio of having another mistress, throws the handkerchief at him, and exits. Othello recognizes the handkerchief. Cassio races after Bianca.
With Bianca’s appearance, which Iago doesn’t seem to have planned, his scene takes on a life of its own. Again, Bianca’s jealousy provides a foil to Othello’s own, while also further convincing Othello that Iago is telling the truth.
Othello comes out of hiding and promises to kill Cassio. But it is less easy for him to think about killing Desdemona. He keeps remembering what a kind, beautiful, talented, and delicate person she is. But Iago convinces him that these qualities make her unfaithfulness all the worse. Othello, at Iago’s prodding, says he will strangle Desdemona in her bed. Iago promises to kill Cassio.
Othello still shows the residue of the tenderness that he and Desdemona eloquently expressed for each other in earlier scenes. But Iago turns this logic on its head, arguing that in Desdemona, as in all women, such attractive or noble traits are in fact just hiding a devious sexuality that threatens to steal men’s honor and manhood.
Just then, Desdemona enters with Lodovico, an envoy who is carrying orders from the Duke of Venice that Othello is to return to Venice and leave Cassio behind to govern Cyprus. Desdemona mentions to Lodovico the falling out between Othello and Cassio, and how much she wants to heal it. This enrages Othello, and he strikes Desdemona and commands her to leave. Lodovico is shocked, and asks that Othello call Desdemona back. Othello complies, but then condemns her as a loose woman and sends her away again. He promises to obey the Duke’s commands, and then exits himself.
The arrival of Lodovico, like that of Bianca just before, provides yet another serendipitous addition to Iago’s plan. The presence of Lodovico as an emissary from Venice also reinforces how dramatically Othello has changed from the early scenes in Venice. Jealousy and the fear that he has been cuckolded have robbed him of his honor, and he now acts recklessly, angrily, and without self-control.
Lodovico can’t believe that Othello, renowned for his unshakable self-control, would act this way. He asks Iago if Othello has gone mad. Iago refuses to answer, but clearly implies that something seems to be terribly wrong with Othello, and advises Lodovico to observe Othello for himself.
Iago quickly assumes control of this new dimension of the situation. Once again, Iago refuses to answer questions in such a way that makes him look loyal while at the same time inspiring the beliefs he wants his interlocutor to have.