Othello tells how Iago, ensign to the Moorish general Othello, convinces his chief that his wife, Desdemona, betrays him with the lieutenant Cassio, until Othello kills her and discovers, too late, that everything was a lie.
In Act I, in Venice, Iago and Roderigo wake the senator Brabantio to warn him that his daughter has run off with the Moor, and Iago confesses to Roderigo that he serves him only out of convenience. In the Senate, Othello defends himself against the charge of witchcraft by telling his own life, Desdemona confirms the marriage, and he sets off for Cyprus against the Turks, with his wife under Iago's escort. In Act II, the storm sinks the Turkish fleet, Iago makes Cassio drink, and Cassio loses the lieutenancy.
In Act III, Scene 3, Desdemona promises to intercede for Cassio, Iago insinuates doubts to Othello, and the handkerchief she drops finds its way into Iago's hands through Emilia. Othello demands ocular proof, and Iago answers with a dream he attributes to Cassio and with the handkerchief he says he saw with him. In Act IV, Othello falls into a fit, hears Iago and Cassio talk about Bianca and takes their laughter as a confession, decides to strangle his wife and slaps her in front of Lodovico.
In Act V, Iago sends Roderigo to kill Cassio, wounds Cassio from behind and stabs Roderigo. Othello smothers Desdemona, Emilia reveals that she was the one who gave the handkerchief to her husband, Iago kills her and flees, and Othello, learning the plot, kills himself beside his wife.