Iago decides to use this handkerchief against Cassio. Iago plants it in Cassio’s room, in plain site for Cassio to find. Iago believes that Othello will fall for this and believe that Desdemona is seeing Cassio. Iago is going to get Cassio to talk about Bianca but Othello will think Cassio is talking about Desdemona. Cassio asks Bianca to make a copy of the handkerchief, unknown that it belongs to Desdemona. Bianca is jealous because it is another woman's and she has strong feelings for Cassio. Cassio explains to Bianca that he found the handkerchief in his room. Later in the play, Bianca and Cassio are talking, and Othello is in the corner listening. Bianca brings the handkerchief, which is lucky for Iago’s master plan. Bianca gives the handkerchief back to Cassio and tells him that she will not copy it. Ultimately, when Othello sees Cassio with the handkerchief, he believes that his love-gift to Desdemona is worthless. This is the ocular proof that Othello needed. Iago states to Othello, “Yours by this hand. And to see how he prizes the foolish woman your wife! She gave it him, and he hath given it his whore” (Shakespeare 4.1.141-43). Iago is telling Othello that Desdemona was unfaithful and gave the handkerchief to Cassio who then gave it to his whore, Bianca. With this knowledge, Othello orders Iago to kill Cassio that night, and he on the other hand will kill