Othello and Iago enter and they speak to each other. They discuss what Desdemona may have done behind Othello’s back. Iago fibs to Othello and says that he has heard Cassio speaking about being with Desdemona. Othello works himself into such a rage that he falls to the ground in an epileptic attack. Cassio comes by to try to help. As the attack wears off, Iago suggests that Cassio leave the area. Later, Iago plans to meet up with and talk to Cassio one on one.
Cassio leaves the area. Upon regaining his bearings, Iago points out to Othello how it’s better that he know the truth about his wife than live in the dark. Iago remarks on how Cassio came by and how they made plans to meet up to speak to each other later. Iago suggests to Othello to go off and hide while he converses with Cassio. Iago will get Cassio to confess about his affair, while Othello gets to observe everything from his hiding spot. Othello agrees to the plan and he leaves to hide.
Cassio enters. Iago gets him to speak up about his relationship with Bianca. Although Othello cannot hear the conversation from where he hides, he is able to see the expressions on Cassio’s face as he speaks. Othello assumes that he is speaking of his affair with Desdemona. Othello grows angry as he observes the manner in which Cassio is talking.
Bianca interrupts their conversation. She returns the handkerchief that Cassio had handed to her. Othello, still watching from afar, is stunned to see Desdemona’s handkerchief. Bianca then invites Cassio to dinner later. She leaves and Iago encourages Cassio to go after her. He does so.
Once Cassio is gone, Othello comes out of hiding. He asks Iago how he should kill Cassio. Othello also plans to kill Desdemona for her infidelity. Iago suggests that he strangle Desdemona to death. Iago, himself, will be the one to kill Cassio.
Their conversation is interrupted by the arrival of Lodovico and Desdemona. Lodovico is Desdemona’s cousin and he works for the Duke. He greets Othello and bids hello from the Duke and the senators. He hands Othello a letter.
Iago welcomes Lodovico to Cyprus. Lodovico asks how Cassio is doing. Upon bringing up Cassio, Desdemona asks for Lodovico’s help in fixing the issue between Cassio and Othello. She says that she wants to fix the problem on account of the love she bears for Cassio. Othello doesn’t react well to this remark.
Lodovico says that they are calling upon the return of Othello to Venice. Cassio is to take over for Othello in Cyprus. Desdemona is happy to hear of the promotion Cassio is going to receive. Othello, not too happy with Desdemona’s happy reaction, slaps her. Lodovico cannot believe what has just happened. Desdemona leaves. Othello soon leaves too.
Lodovico questions Iago on Othello’s mental well-being. He doesn’t understand what could have happened to put the well-regarded Othello into such a bad state. Iago urges Lodovico to observe Othello to see what type of a person he has become.