Iago continues his insinuations when speaking to Othello; he provides more "proofs" that are anything but, though Othello has calmed, and seems more troubled and less angry. In the last act Othello was trying to act as Desdemona's defender, and Iago was the accuser; ironically, they seem to have switched places here, and Iago seems to be defending Desdemona, all while producing more "evidence" to condemn her. The handkerchief, however, is as important a symbol as ever; Othello says, "it comes o'er my memory as a raven doth over an infected house" (IV.i.20-21). The handkerchief is an omen of the destruction of their marriage.