Desdemona has her moment of truth inOthelloin the last act, just before she is murdered by her jealous husband, who has been totally deceived by the villainous Iago. For the first time in the play Desdemona understands that Iago has been plotting against her and Cassio, and for the first time she realizes what has become of her lost handkerchief. This understanding comes about during the following exchange between husband and wife.
By heaven, I saw my handkerchief in's hand!
O perjured woman! thou dost stone my heart,
And makes me call what I intend to do
A murder, whiich I thought a sacrifice.
I saw the handkerchief.
He found it then.
I never gave it him. Send for him hither.
Let him confess a truth.
He hath confessed.
He will not say so.
No, his mouth is stopped.
Honest Iago hath ta'en order for't.
O, my fear interprets. What, is he dead?
Had all his hairs been lives, my great revenge
Had stomach for them all.
Alas, he is betrayed, and I undone! (V.2)
The exact moment of truth for Desdemona comes when Othello tells her that Cassio is dead. She realizes that she has no way of proving her innocence and that she is sure to die herself. She also realizes the true character of Iago--something which Emilia and Othello have yet to learn.