Iago and Roderigo make their way over to Brabantio's palace. They wake him up through the window and Roderigo convinces Brabantio that his daughter (Desdemona) has run away with Othello. Iago stands there smirking, knowing that his evil plan is working. Brabantio is continuously trying to separate Othello and Desdemona, however is unsuccessful. A war breaks out in Cyprus so Othello and Cassio are sent over to fight.
Iago, Desdemona and Emilia arrive in Cyprus and Cassio greets. Othello arrives later; he is happy to see Desdemona. Iago convinces Roderigo to attack Cassio later. Iago sits Cassio down and gets him to drink. He tries to get him to fall for Desdemona, however this plan doesn't work, but Cassio proceeds to fight Roderigo. Montano tries to stop Cassio, but Cassio just hurts him. Othello comes outside and finds out what is happening, and strips Cassio of his title
Cassio bids a clown to see if Desdemona will speak to him. Iago enters, Cassio says that he wants to speak to Desdemona, so she can explain everything to Othello. Emilia comes out and tells Cassio to speak to Desdemona. She forgives Cassio and speaks to him briefly. Iago then manipulates Othello and tells him that Desdemona is having an affair with Cassio. Iago shows further proof by saying that Desdemona dropped the handkerchief Othello gave her. Othello swears to kill Cassio.