Othello has allowed Iago's deceit to turn him into a man with crazed jealousy. Othello believes Iago over his wife. Iago is a shrewd villain. He plants seeds of jealousy in Othello. Iago is an evil person.
Desdemona is a virtuous wife who appears to be having an affair with Cassio. Cassio is only interested in being reinstated to his former position as lieutenant. Cassio asks Desdemona to plead to Othello for his former position. Both Desdemona and Cassio are innocent, but Iago twists their actions into something else. Othello reacts as a man who has been consumed with jealousy:
In the end, Othello is so convinced by Iago's manipulation that he murders his wife in their bed.
Roderigo has been used by Iago to further his deceitful plan to create jealousy in Othello. Roderigo allows his own jealousy to create trouble. Roderigo falls into Iago's hand. Roderigo's anger and rage causes him to fight with Cassio. Roderigo loses his life in the end. Iago kills him as part of his plan.
Emilia furthers Iago's plan by giving him the handkerchief that belongs to Desdemona. Emilia realizes the error of her deed after it is too late. She declares Desdemona's innocence after Othello has murdered his wife. Emilia then reveals that Iago is the culprit who has designed an evil plan. Iago kills Emilia in a rage.