The audience know about Iago’s plan of betrayal because he keeps repeating how much he hates the Moor. "I hate the Moor. .... ", this is called dramatic irony where the audience know what Iago is planning to do to Othello even though the characters in the play don’t realise what Iago is up to. Iago uses his so called ‘loyalty’ to Othello to pull him in and make him believe what he is saying about Desdemona.
Iago appears to be very reluctant about speaking badly of others while at the same time telling Othello all the wrong that others are doing towards him. By Iago doing this he is being sneaky and very smart because it makes Othello think that he is trying to be loyal to his friends and that he himself should feel guilt for trying to pull the information out of him. Iago stresses that Cassio is his “worthy friend”; in other words, one does not lie about his friend. This is an example of Iago manipulating Othello because he is pretending to be loyal to his friends and not wanting to talk about them badly but he says it anyway.
When Emilia comments that the tension between Othello and Cassio “grieves her husband…as if the cause were his” we see how Iago has managed to play his own wife who doesn’t know the wrong that Iago is thinking. This is another example of dramatic irony where the character isn’t aware of important information that the audience or reader is. This is also an example of Iago manipulating his wife into believing him.
When Othello and Iago enter Iago says “ha I like not that!” this is reference to Cassio leaving. Othello asks if that was Cassio he saw departing his wife and Iago answers with pretend hesitation that he thinks not “that he would steal away so guilty like” suggesting that there is something wrong in Cassio’s visit with Desdemona.
The conversation that follows between Othello and Iago has a lot of half thoughts and insinuations by Iago to raise Othello’s suspicions about Cassio. As they speak, Othello comments how Iago “didst contract and purse brow together, as if then shut up in brain, some horrible conceit” Iago carefully analyses Othello's statement to generate more curiosity in him and prompt Othello to say “show me thy thought” this gives Iago the opportunity to plant his “worst of thought” in Othello’s mind.
Iago replies with the warning to “beware, my lord, of jealousy, it is the green eyed monster, which doth mock the meat it feeds on”. Nobody talks about jealousy before this so Iago is implying that Othello is jealous. When Othello seems to be doubtful about there being anything to be jealous of, “for she had eyes and chose me” he says to Iago “when I doubt, prove.” To weaken Othello’s confidence, Iago replies “observe her well with Cassio… I know our country disposition well”.
Iago takes that opportunity to play on the fact that Othello is in denial by suggesting that he is not aware of the deceptive ways of his “Venetian woman.” He adds, “She did deceive her father, marrying you” so much so that Brabantio “thought t’was witchcraft.” Iago is still manipulating Othello into believing that she can deceive once then she will deceive again without actually telling him that he thinks that she has been deceived.
The conversation that they have, leaves Othello in a terrible and emotional state, so when Desdemona enters, he tells her he has a headache, and she replies , “Let me bind it hard” with her handkerchief, the “first remembrance from the Moor.” He pushes the handkerchief away, and it falls to the ground. Emilia picks it up and later gives it to her husband Iago. This gives him the “ocular proof” that Othello asked him for to prove Desdemona’s unfaithfulness.
In the soliloquy, Iago recognizes the effect he is having as “the Moor already changes with my poison.” Iago continues the metaphor that he created in Act 2 Scene 3 when he compared his lies to a pestilence he would pour into Othello’s ear. At this point it can be seen that Iago has definitely got Othello on side and got him really jealous so much so to the point where Iago believes that “not poppy, nor mandragora, nor all the drowsy syrups of the world shall ever medicine thee to that sweet sleep” which basically just means that Iago is convinced that Othello will never be able to sleep peacefully again. Othello is now using Othello’s sorrow for his happiness. You may say that Othello has taken a lethal dose of Iago’s poison!
When Othello returns, it is clear that he is being troubled by his doubts of Desdemona this is clear from his remark, “Ha! Ha! False to me?” Iago’s poison is getting comfortable so to say in Othello’s mind.
This Scene represents a turning point for Othello as he is on the borderline of doubt and uncertainty with respect to Desdemona’s unfaithfulness and Iago's honesty. This is the point of weakness Iago needs to ensure that his devious plan will work. Iago says that Othello is “eaten up with passion” and he keeps on going about Cassio and Desdemona. Iago abuses Othello’s trust by pretending to be so honest that it pains him to tell Othello that he heard Cassio cry out, “sweet Desdemona!” in his sleep. From this Othello’s anger turns into a threat to “ tear her to pieces” then Iago goes lower than low by saying “she may be honest yet” after all the hard work he has done he takes a risk by telling him that she still may be innocent and hoping that he doesn’t believe him. This is being two-faced, because he then says that he saw Cassio wiping hi beard with Desdemona’s handkerchief. Given the importance of the handkerchief to Othello it isn’t at all surprising that Othello’s anger turns to the feeling of wanting revenge which in a way is still anger.
Iago has manipulated Othello in so many ways throughout this Scene. The Scene makes sure that Iago is shown to be a manipulative evil man. This Scene sets up the rest of the play to be a tale of deceit, people acting and not being themselves. The plot’s main theme seems to be trying to get the message across that most of the times; people are not what they seem to be. Othello is very gullible in this Scene as he doesn’t do his own research to find out what is really going on. He just trusts Iago and turns to him for advice and directions at every point throughout the Scene.
At the end of the play Othello kills Desdemona and then Emilia comes in and sees what has happened and cries for help. Montano, Gratiano and Iago come and see her dead and ask what happened. Emilia says that the Moor has killed her mistress. Cassio is standing there on crutches. Othello tells them why he killed her and Cassio denied it all. Then Emilia tells Othello what really happened with the handkerchief and Iago kills her for talking. She asks one of the men who catch her when she falls to lay her next to her mistress. Then Othello goes to stab Iago and succeeds but doesn’t kill him, “I bleed sir, but not kil’d.” Othello speaks to Montano, Gratiano recalling his service to Venice and stating that he did not love wisely, but loved too well. He recalls an incident when he engaged a Turk for beating a Venetian citizen, illustrating the Act ion with his sword; he stabs himself and falls dead upon the bed.
In the last Scene of the play Iago may seem to have succeeded in the beginning but ends up being punished for his wrong doings. His wife turns on him and tells Othello of all his wrong doings. Therefore his conspiracy was revealed because he failed to silence his wife Emilia and Cassio.
