1.2 Brabantio and armed officers appear to arrest Othello for using witchcraft on Desdemona, but Othello, with a summons to the Duke's war council, has them all go to the Duke.

1.3 Brabantio presents his accusations, Othello denies them, and Desdemona states her love for her husband. Brabantio rejects his daughter. Othello accepts his charge from the war council and sails to war with Desdemona following. Iago consoles Roderigo and, alone, plans revenge on Othello by making him jealous of Cassio.

 2.1 A terrible storm has destroyed the threat to Cyprus of the Turkish fleet. Othello arrives and is happily reunited with Desdemona. Iago convinces Roderigo to pick a fight with Cassio later that night. Alone, Iago is certain that Cassio and Othello have both made love to his wife Emilia.

2.2 Othello calls for a holiday celebrating the destruction of the Turkish fleet and his wedding to Desdemona.

2.3 Iago and Roderigo lead Cassio to start a drunken fight with Montano. Iago's story, told with apparent unwillingness, convinces Othello to fire Cassio. Iago urges Cassio to seek Desdemona's help in regaining his place.

3.1 Iago helps Cassio gain a personal and private meeting with Desdemona.

3.2 Othello, busy with important letters to Venice, tells Iago to meet him later.

3.3 Desdemona promises to help Cassio regain his place. Iago begins to make Othello jealous by dropping hints, while protesting that he will not tell unfounded suspicions against his good friend Cassio. Desdemona enters, unsuccessfully attempting to soothe Othello's "headache" with the handkerchief given to her by Othello. When she drops it, Emilia finds it and gives it to Iago. Othello re-enters, determined to make Iago prove his suspicions. Iago tells Othello that Cassio talks in his sleep of making love to Desdemona and that he wipes his face with Desdemona's handkerchief. Othello names Iago as his new lieutenant.

3.4 Desdemona again begs Othello to reinstate her friend Cassio, but Othello angrily asks for the handkerchief. Cassio meets with Bianca, his mistress, who scolds him, but agrees to copy a handkerchief Cassio has found in his room (left there by Iago).

4.1 Iago goads the enraged Othello by having him eavesdrop on Cassio.  Although Iago questions Cassio about Bianca, Othello thinks they are discussing Desdemona. Bianca enters, telling Cassio she refuses to copy another woman's gift. Othello rages at the now undeniable proof of Desdemona's infidelity. Othello plans to strangle Desdemona, and orders Iago to murder Cassio. Venetian gentlemen arrive with orders for Othello to return to Venice and Cassio to remain as governor of Cyprus. Othello hits and humiliates Desdemona before the Venetians.

4.2 Othello questions Emilia and Desdemona but will not believe their defense of his wife's fidelity. Desdemona asks Iago how she might clear her name to Othello. Roderigo, fed up with Iago, threatens to go to Desdemona, but Iago distracts him in a plot to murder Cassio.

4.3 Othello orders Desdemona to their bed unattended. She sings the "Willow Song" and incredulously hears Emilia's views on adultery.

5.1 In Roderigo's attempt to murder Cassio, both men are wounded. Iago secretly kills Roderigo and casts suspicion for the attack on Bianca.

5.2 Othello strangles Desdemona. Emilia denies Othello's charges against his wife, even defying her husband's order to be silent. Iago kills Emilia, and Othello wounds Iago. The true story unfolds. Othello, convinced of his mistake, executes himself, kissing Desdemona as he dies.