Midway through Act 4, Scene 1, and prior to Bianca's entrance, Othello has been secretly observing a bawdy discussion between Iago and Cassio about the latter's sexual exploits with a young woman. Thanks to Iago's impeccable planning (and some bad luck), neither speaker mentions the name of the woman in question; it is in fact Bianca, but Othello tragically assumes it to be his wife, Desdemona. Bianca suddenly enters, and her suspicions of Cassio are even greater than before. She is convinced that the handkerchief belongs to another woman, and throws it contemptuously at Cassio's feet. In Othello's eyes, her apparent jealousy confirms his wife's infidelity. This "evidence" completes Iago's manufactured case against Desdemona, and thereafter Othello is determined to murder both her and Cassio.