ACT I - THE EXTERIOR OF THE CASTLE
It is evening: a storm is raging. The citizens and soldiers are awaiting Otello's return from the war against the Turks. Among those in the crowd we find Jago, Roderigo, Cassio and Montano. Otello's ship is in distress: the chorus raise their voices to Heaven in prayer (Dio fulgor della bufera). Jago and Roderigo alone do not share the general anxiety. At last the ship is safely harboured. Otello disembarks, announces their victory (Esultate!) and then enters the fortress (chorus: Vittoria! Sterminio!). The storm shows signs of subsiding. To one side, Jago and Roderigo start to hatch a plot. Roderigo is secretly in love with Desdemona; Jago promises to help him win her, and tells Roderigo of his hatred of Otello who has appointed Cassio as captain instead of him. As the two move off, Jago starts to illustrate his plan. The citizens and soldiers have lit a fire to celebrate the victory (chorus: Fuoco di gioia!). Jago tries to get Cassio drunk: he invites him to drink to the marriage of Desdemona and Otello and thus Roderigo's jealousy of Cassio is aroused. He then proposes a toast (Innaffia I'ugola) in which everybody joins. Soon Cassio is drunk, and when Montano comes to call him for his turn on watch, he is incapable of obeying him. Roderigo then provokes Cassio, and a scuffle breaks out. Jago fans the flames sending Roderigo off to the town to raise a general alarm.
The brawl is interrupted by the arrival of Otello. Jago Cassio drunk and Montano wounded, demotes protests his innocence; Otello, angry at finding Cassio, and then orders everyone to depart.
Otello and Desdemona, left on their own, join together to sing of their love for each other in a powerful duet (Giá nella notte densa). Reflecting on Otello's tales of war, their thoughts turn to Desdemona's sympathy for his misfortunes. It is full night, the sky has cleared. Otello and Desdemona kiss ecstatically. Ten, embracing, they move off towards the castle.
ACT II - A HALL ON THE GROUND FLOOR OF THE CASTLE
Jago continues his scheming. He advises the disgraced Cassio to ask Desdemona to intercede for him; Cassio goes to wait for her in the Garden.
Jago, now all alone, reveals all his evil treachery (Credo in un Dio crudel). Desdemona comes into the garden followed by Emilia. With great satisfaction, Jago observes Cassio approach Desdemona and notes the friendliness with which she greets him.
Otello arrives. Jago pretends not to see and KLÁRA shows slight annoyance at something. Otello notes the conversation between Cassio and Desdemona. Jago, by cleverly dwelling on the subject of Cassio, succeeds in arousing Otello's suspicions to such an extent that he bursts out in a fit of anger and jealousy against Cassio and Desdemona. In the garden, Desdemona is surrounded by women, youths and sailors who offer her flowers and gifts (chorus: Dove guardi splendono). Her grace and charm move Otello, who for an instant forgets his suspicions.
Desdemona goes up to Otello and speaks in favour of Cassio. Otello sees his suspicions confirmed and violently pushes her away from him. Otello, Desdemona, Jago and Emilia begin to sing a quartet: Desdemona tries to make it up with Otello (Se inconscia, contro te, sposo, ho peccato), who in fact considers himself betrayed and derided (Forse perché gli inganni); Jago argues with Emilia for the handkerchief dropped by Desdemona and finally seizes it from her.
Otello, alone with Jago, gives vent to all his desperation. Jago pretends to reassure him, thus bringing about another fit of anger. Otello weeps for his ruined life and disgraced glory (Ora e per sempre addio, sante memorie). Otello is in need of proof: as Jago shows signs of drawing back, Otello, mad with rage and suffering, rushes at him. Jago by now has achieved his goal: Otello is in his hands and ready to believe his every word. Jago tells of having once heard Cassio express his love for Desdemona's handkerchief in Cassio's possession. Otello has no more doubts and swears revenge (Si, pel ciel marmoreo giuro!); Jago promises to stand by him and seals their union by repeating the oath.
ACT III - THE GREAT HALL OF THE CASTLE
A herald announces to Otello that the galley bringing the Venetian ambassadors is approaching the port Jago undertakes to make Cassio speak so that Otello, who has concealed himself, can discover the truth. Jago goes out and Desdemona enters.
The discussion between husband and wife, at first affectionate, rapidly becomes violent. Desdemona turns the conversation to Cassio, thus aggravating Otello's jealousy. Otello asks her for the handkerchief which Jago has mentioned to him. Desdemona does not understand the great importance, which Otello attaches to the handkerchief, continues to insist in favour of Cassio and thus worsens the situation. Otello accuses her of being unfaithful and insists on her justifying herself by swearing on oath. Otello's terrible threat upsets her (Esterrefatta fisso lo sguardo tuo tremendo): her pleading succeeds only in changing Otello's violence into ruthless sarcasm.
Otello, alone, yields once again to desperation (Dio! mi potevi scagliar tutti i mali).
Jago enters, followed by Cassio. Otello hides.
Believing that he is alone with Jago, Cassio allows himself to be talked into a ribald gallant conversation: the subject of his discussion is Bianca, the woman he is in love with, but Jago makes sure that Otello is able to catch only apart of their conversation and that he is led to believe that Cassio is talking about Desdemona. Cassio shows Desdemona's handkerchief which Jago has secretly planted in Cassio's house. From his hiding place, Otello sees the handkerchief, to him the decisive proof of Desdemona's infidelity. Jago (Questa é una ragna dove il tuo cour) urges Cassio to brag about this mysterious gift, a token of his successful conquest. A fanfare of trumpets is heard, then a cannon shot. The ambassador's ship has reached port. Cassio leaves.
From outside, trumpets and loud applause announce of Desdemona's guilt: Jago suggest that Otello kill her the arrival of the ambassadors. By now, Otello is certain that same night, while he himself will attend to Cassio.
The hall fills up. Lodovico enters, followed by dignitaries, other gentlemen and ladies, soldiers and trumpeters. He brings Otello a message from the Republic. In the conversation, which begins, Desdemona speaks of her affection for Cassio, thus exasperating Otello who rushes at her and strikes her in full and horrified view of the assembled company.
Othello reads the message from the Doge. He announces that the Republic has recalled him to Venice and appointed Cassio as his successor to govern Cyprus. Desdemona breaks into tears, which Otello sees as a sign of her suffering through separation from her lover. Mad with rage, he violently flings her to the ground. Desdemona's desperate words (A terra! Si... nel livido fango...) start off a great ensemble in which everyone expresses shock and compassion. Jago busies himself with his plans, kindling Otello's rage and convincing Roderigo to kill Cassio before dawn. In a fit of anger, Otello orders everyone to leave. Jago succeeds in convincing everybody that Otello is mad, and all go off horrified.
Otello, again alone with Jago, is distraught and faints. While fanfares and voices heard outside acclaim Otello, the triumphant Jago points to his victim with a cruel gesture of contempt.
ACT IV - DESDEMONA'S BEDROOM
Desdemona, helped by Emilia, prepares herself for bed. Maid comes to mind, and she repeats the sad Willow She is disturbed by portents of death. Her mother's Song, which she used to sing (Piangea cantando).
Desdemona, left alone, recites her evening prayers (Ave Maria), then goes to bed.
Otello enters. He observes Desdemona in her sleep, shows his rage, then kisses her three times. Desdemona wakes up. Otello orders her to prepare for death. Desdemona's pleading and declarations of innocence are to no avail. He suffocates her. A knock is heard at the door: it is Emilia who brings news of the death of Roderigo, killed by Cassio. With her last breath, Desdemona proclaims her innocence. Emilia, horrified, shouts for help.
Lodovico, Cassio and Jago run to the scene. Emilia reveals the deception of the handkerchief. Montano, who has arrived with men-at-arms, confirms that Roderigo has incriminated Jago with his dying breath. Jago flees. For Otello, the final moments have come (Niún mi tema): heartbroken, he draws a dagger and stabs himself, dying as he makes a last attempt to kiss Desdemona's corpse.