Desdemona pleads for Cassio
Iago insinuates that Desdemona is unfaithful
Othello becomes jealous
Desdemona drops her handkerchief, which Emilia gives to Iago
Iago plants it with Cassio
Othello demands proof of Desdemona's infidelity
Iago lies about seeing Cassio with the handkerchief, driving Othello to rage