In a conversation with Othello, Iago says that Cassio has confessed to sex with Desdemona. This revelation is too much for Othello, who becomes incoherent and faints. When Cassio enters, Iago claims that Othello has epilepsy and has had seizures before. Rather than revive him, they must let the fit take its course. Iago sends Cassio away, telling him to come back later. Othello, regaining consciousness, talks of himself as one among many cuckolds, but Iago tells him to hide and observe Cassio, who is returning. Iago says he will draw Cassio out to tell of his amorous adventures with Desdemona.
Othello withdraws, too emotionally involved to understand that Iago is manipulating him, and Iago talks with Cassio about Bianca. Othello sees his smiles and laughter but cannot hear the details and believes he is joking about how much Desdemona loves him. Then Bianca herself enters, with Desdemona's handkerchief, which she throws back at Cassio. Seeing his wife's handkerchief in the hands of Cassio's mistress is, for Othello, the "ocular proof" he sought. He is now convinced of Desdemona's infidelity and knows he must kill both Cassio and Desdemona that very night.
Iago, while pretending to reassure Othello, is rubbing salt into his wounds. Their conversation is of hypothetical acts, whether they constitute betrayal or not, but Othello imagines them all being acted out by Desdemona and Cassio. But this is just the warm-up to the topic that Iago has discovered can most easily rouse Othello's passions: the handkerchief. Othello, in his thinking, assumes it is a symbol for his wife's honor, but Iago plays at thinking it is only a handkerchief: "being hers, she may, I think, bestow't on any man" (13). He repeats again the word "handkerchief," and Othello cries out.
Iago can see that Othello is at the edge of madness, and there is no way he can judge just how far to push him, considering his unexpectedly violent previous reaction. However, Iago cannot afford to leave Othello in his present frame of mind, where he might do something unpredictable. Therefore, he proceeds to tell Othello the direct lie: that Cassio has confessed to a sexual affair with Desdemona. Iago uses again the successful technique of hesitation, forcing Othello himself to say what Iago would have him think. Iago, the liar, comes back to the word "lie" when telling his untruth so that the word "lie" echoes with double meaning through their conversation, lacerating Othello with thoughts of two illicit lovers and, at the same time, accusing Iago for his abuse of the truth.
Othello is now raving; his words come in an anxious jumble around "handkerchief," and "confess" until he falls down in a faint. The overstressed mind seeks refuge in unconsciousness. Instead of pity or alarm, Iago only expresses satisfaction that his medicine (poison words) is working.
Cassio suggests rubbing Othello about the temples, but Iago calmly waits for him to regain consciousness and takes the opportunity to tell Cassio that Othello has epileptic seizures and bouts of madness. Such a story is Iago's insurance, in case Othello should later say something that Cassio finds strange.
Iago urges Othello to hide and watch him talk with Cassio. Othello, who had led armies into battle, is now reduced to crouching behind something, listening to a conversation he cannot well hear, and imagining Cassio and his wife laughing at him. Iago takes a great risk with this maneuver, as he has no way of controlling completely what Cassio might say or how much Othello actually overhears. He leads Cassio to laugh and joke about Bianca, trusting that Othello's mind will turn what he sees into evidence. Then, by chance, Bianca walks in with the strawberry-spotted handkerchief and berates Cassio for asking her to copy the token of his new love. Othello recognizes the handkerchief, and all other considerations are forgotten.
Othello goes directly to the point: "How shall I murder him, Iago?" Othello swears also to kill his wife this night, he curses her and weeps over her at the same time, mingling love and murder: "for she shall not live; no, my heart is turned to stone . . . " (178-179).
This is the second time Othello has sworn to kill both Cassio and Desdemona, but his continuity of love beside revenge unnerves Iago, who needs to push Othello to a definite unalloyed commitment to murder. Therefore, Iago prompts Othello to consider his personal honour: "If you be so fond over her iniquity, give her patent to offend, for if it touches not you, it comes near nobody" (199-201). The idea of giving his wife permission to take lovers so enrages Othello that he cries, "I will chop her into messes" (202), surely the most savage of all his threats, and one he later regrets.
Still Othello knows the pull of love and asks for poison so that he might kill her at a distance, but he sees justice in Iago's idea of strangling her in her bed, imagining that she has dishonored that bed. Again the agreement is made: Iago is to kill Cassio, and Othello is to kill Desdemona. Iago has profited from good luck and good organization to achieve almost complete power over Othello.
Lodovico, Desdemona's cousin, has just arrived from Venice with a letter for Othello. Expecting to see a happy newly married couple, Lodovico finds they can hardly speak to each other. When Othello strikes his wife, calling her "Devil" (235), Lodovico is shocked, but whatever he might say would only make things worse. Othello and Desdemona are involved in a personal matter to the exclusion of others, and Othello is fraught by a matter of internal conflict that excludes his wife. From the outside, it all looks like madness. Lodovico is amazed at the change in "the noble Moor . . . whose solid virtue / The shot of accident, nor dart of chance, could neither graze, nor pierce" (260-264).
Iago knows that Othello has been ordered back to Venice and Cassio has been made commander in Cyprus, so he knows the murders must be done immediately, or he will be found out. He hints to Lodovico that Othello should be watched, increasing Lodovico's suspicion that Othello is going mad.
infected (21) stricken with the plague.
convinced or supplied (28) overcame or gratified.
A horned man's (63) a cuckold's.
ecstasy (80) a trance.
encave (82) hide.
spleen (89) anger.
unbookish (102) uninformed.
caitiff (109) a wretch.
customer (120) here, a prostitute.
hales (140) tugs at; hauls.
fitchew (146) a polecat (meaning "a whore").
hobby-horse (156) a prostitute; harlot.
undertaker (156) a person who undertakes to do something.
crocodile (247) a reference to the false tears supposedly shed by crocodiles.