Iago and Rodrigo plan to tell Brabantio (Desdemona's father) that her and Othelllo had eloped. Brabantio is furious and sends his guard to go capture Othello.
Act 2, Scene 2
Othello, Brabantio, Iago and Roderigo all arrive at the Duke's meeting. Brabantio accuses Othello of using black magic. Although, the duke needs Othello to stop the Turks from taking over Cyprus.
Act 3, Scene 1
A soldier enters, claiming that the Turks drowned in a storm. Cassio tells them that Othello's ship is stil at sea. After hours of waiting Othello returns, and reunites with Desdemona. Iago is ordered to watch over the city, therefore taking action to his plan.
Act 3 , Scene 2
Iago starts to plant seeds of suspicion which were dormant in Othello's mind. Since Othello was already an easy victim of jealousy; it wasnt hard to manipulate him. What Iago was doing was telling othello to beware of jealousy, using reverse psychology.
Othello gave Desdemona a handkerchief, a family heirloom passed down from his mother to his bride. Iago uses his wife, Emilia, to take the handkerchief and plant it in Cassio's room. His wife had no idea what Iago's intention was.
Desdemona looks for the handkerchief and cannot find it, therefore causing her to lie- as she knows how much it means to Othello. This makes Othello suspicious.