Iago convinces Roderigo to follow Desdemona to Cypres in a final attempt to claim her heart. Yet in reality, Iago plans to use Roderigo in his plot to ruin Othello, Desdemona's husband.
Iago devises a plot where he will convince Othello that Desdemona and Cassio have an affair. In order to make the story as believible as possible, Iago encourages flirting between Desdemona and Cassio.
Iago convinces Roderigo to start a fight with Cassio. After Montano is dearly injured, Iago regretfully tells Othello that Cassio is to blame. Striped of his rank, Cassio pleads to Iago for help.
Iago tells Cassio to plea to Desdemona. That hope is not lost. Leading Cassio deeper into the plot of his general's demise.
Iago tells Othello that he believes that his beloved has an affair with Cassio. Enraged Othello demands proof. So Iago tells him that he saw Cassio with Desdemona's hankercheif and to ask his wife about it.
Othello confronts his wife and demands to see the handkerchief he first gave her. When she changes the subject to Cassio. Othello then feels sure of the affair, making him an easy victim for Iago.