The play opens in Venice where two men are having an argument. Rodrigo is angry with Iago because Iago’s boss has married Desdemona, the woman who Rodrigo was paying Iago to help him woo. Iago is angry with Othello too because he wanted a promotion but Othello gave it to Cassio. Iago and Rodrigo alert Brabanzio (Desdemona’s father) to her marriage and they insinuate that the couple is making love at Othello’s house.
Brabanzio is enraged that his daughter has married Othello and accuses him of witchcraft. He decides to pay Othello a visit so Iago runs ahead to ‘warn’ Othello of Brabanzio’s rage. While they are speaking Cassio arrives with a message from the duke who needs his help on a matter concerning Cyprus. Suddenly Brabanzio arrives and berates Othello who calmly explains the love between himself and Desdemona.
The duke and his men are discussing the Turkish ‘purposes toward Cyprus’ and they fear invasion is imminent. Brabanzio, Rodrigo, Iago and Othello all arrive together. The duke is pleased to see ‘valiant’ Othello but Brabanzio would rather discuss the marriage than politics. The duke and his officers question Othello about the marriage and he tries to persuade them of their love but they decide to ‘fetch Desdemona’ to make sure. Eventually it is decided that their marriage will be recognised. However, because of the coming trouble they must leave and try and sort out the problems between the Turkish and Cyprus.
Rodrigo is incensed and asks Iago for help. Iago assures him that once Desdemona has satisfied her lust she will probably see the error of her judgement and marry Rodrigo. Iago hatches a plan that will hurt Othello and Cassio as well as helping Rodrigo. He decides that to break up the marriage he will ‘abuse Othello’s ear/ That [Cassio] is too familiar with his wife.’ He hopes Othello will think badly of his wife and new advisor.
They all arrive in Cyprus the next morning. Cassio is very admiring of Desdemona but is also complimentary of Iago, showing him to be an amiable sort of person. Iago, Emilia (his wife) and Desdemona speak, Iago attempts to compliment the women but Desdemona makes fun of him. Cassio says ‘you may relish him more in/ the soldier than in the scholar,’ as Iago has military experience but Cassio himself is a scholar and this is one reason he was promoted above Iago. Iago notices that when Cassio says this he takes Desdemona’s hand; to the audience he says he will use this to begin his plot to make Othello jealous. By the end of the scene Iago has convinced himself that Desdemona and Cassio are in love.
Iago arranges for Rodrigo and Cassio to fight that evening at a party. When Montano tries to break up the fight, Cassio stabs him and Othello is called from his marriage bed to deal with the situation. Iago advises Cassio to talk to Desdemona to stop Othello being angry and she agrees to help. Iago explains in a soliloquy that he will frame Cassio.
Emilia steals Desdemona’s handkerchief and Iago plants it in Cassio’s room. He then tells Othello his suspicions; Othello is so upset that he has an epileptic fit. He arranges for Othello to overhear him asking Cassio about the affair. Cassio talks about a prostitute he has been seeing but Othello thinks he is talking about Desdemona, especially when he sees the handkerchief.
Othello decides to kill Desdemona and Iago encourages him to strangle her in bed. Lodovico arrives with Desdemona and calls Othello back to Venice leaving Cassio in charge making Othello even angrier. Emilia tries to convince Othello he is wrong and Desdemona pleads for her life, but Othello calls her ‘false as helI’ and a ‘strumpet’. He seems to calm down but tells her to get to bed and wait for him
Iago persuades Rodrigo that the only way to get Desdemona is to kill Cassio. However he fails and Iago injures Cassio instead. Thinking Cassio is dead Othello returns to Desdemona saying ‘Forth of my heart those charms, thine eyes, are blotted;/Thy bed, lust-stain’d, shall with lust’s blood be spotted.’ Lodovico comes in and sees what has happened to Cassio, Iago pretends to be astonished and kills Rodrigo and helps Cassio with his injuries.
Meanwhile Othello arrives at his bedroom. He makes sure Desdemona has prayed so that her soul will go to heaven. He confronts her about the handkerchief and she pleads her innocence but Othello kills her. When Emilia arrives Desdemona pretends she has killed herself and dies. Iago and the attendants arrive too and see what has happened. Emilia explains that she gave Iago the handkerchief and Iago stabs her. The whole story comes out when a letter is found in Rodrigo’s pocket. Cassio explains himself and is then made governor of Cyprus. Othello stabs himself because he ‘threw a pearl away/ Richer than all his tribe;’ and was tricked.