Scene i: At Iago's insistence, Roderigo attacks Cassio, but fails, and Cassio wounds him instead. Iago sees this, and having little choice, stabs Cassio's leg from behind and runs away. Othello, thinking that Cassio is dead, goes to kill Desdemona. Lodovico and Gratiano hear Cassio's cry for help but are afraid of what might happen to them if they go to him. Iago appears, looking as if he has come from bed, and goes to Cassio. Roderigo calls out for help, and knowing that Roderigo could give him away, Iago kills him. Bianca arrives, and Iago tries to pin everything on her. Emilia then learns that Cassio is wounded, and Roderigo is dead. Iago sends her to deliver the news to Othello and Desdemona.
The final scene begins with Othello delivering a beautiful soliloquy before he murders his wife, showing that he is clearly in love with her but gives into his own weakness; jealousy and pride. As he looks at Desdemona sleep, he has to talk himself into killing her. She wakes and tries to defend herself against these awful accusations, but Othello smothers her. Emelia comes to the door at this climax and Othello lets her in, but he is clearly not himself. Emelia sees Desdemona and starts to yell "MURDER" even as Othello threatens to kill her as well. She tells Othello to do what he will; she will not keep silent. She then tells him of Desdemona's purity and faithfulness. Emelia soon realizes, to her horror, the part she played in this tragedy in stealing that handkerchief. When Othello says that he saw the handkerchief in Cassio's hand, Emilia reveals that she found it and gave it to Iago. Othello then attacks Iago. Iago puts Emelia in front of him, stabs her and runs away. The other men disarm Othello and leave Gratiano to guard him while they pursue Iago. Emilia lays by Desdemona, tells Othello that Desdemona was chaste and true, then dies. Othello is now filled with confusion and grief. Lodovico enters, followed by Montano, Cassio, and Iago. Lodovico questions Othello, revealing even more proof of Iago's guilt, and states that Othello will be sent to Venice for trial. As he is about to be led away, Othello asks for a chance to say "a word or two." He asks Iago why he did this to him, and Iago refuses to say a word about it saying, "What you know, you know." Othello speaks of how he wants to be remembered, then stabs himself, kisses Desdemona, and dies.