Iago (Alberto Gazale, left) sets his scheme in motion, aided unwittingly by Cassio (Sorin Lupu).
The opera is set in a maritime city on the island of Cyprus, at the end of the 15th century. Otello is a Venetian, acting as Governor of Cyprus. ACT ONE opens outside Otello's castle, with a storm raging. On shore is a group of people including Iago, Cassio, and Montano. They wonder about the fate of their leader, Otello, who is sailing towards home after a successful battle. Things look bad, but Otello safely reaches harbor.
As the crowd disperses, Iago and Roderigo confer. Roderigo is in love with Otello's wife, Desdemona — a seemingly hopeless situation for him now that Otello is safely home. Iago reassures his friend that sooner or later, Desdemona will tire of Otello, and Roderigo will have his chance.
Iago then sings about a man he despises, Cassio, whom Iago believes has been unfairly promoted. Going to Cassio, Iago encourages him to get drunk. Roderigo then goads Cassio into a fight, which quickly becomes a brawl. Iago stage-manages everything, then orders Roderigo to sound an alarm. As the situation deteriorates, Otello appears and calms everyone down. He also blames the whole thing on Cassio — just as Iago had hoped.
When Desdemona appears, Otello sends everyone away so he can be alone with her. The two sing a sensuous duet, "Già nella notte densa" — "Now in the dark night." They recall how they first met, then quietly walk into Otello's castle together.
Inside the castle, as ACT TWO begins, Iago hints at his plans in a conversation with Cassio. Iago suggests that Cassio might approach Desdemona, and enlist her help in getting back in Otello's good graces. When Cassio leaves to find Desdemona, we get a terrifying glimpse at Iago's true nature, in his monologue, "Credo in un Dio crudel" — "I believe in a cruel God."
Iago notices his wife Emilia in the garden, with Desdemona, and watches as Cassio approaches the two women. Otello then enters, and Iago urges him to watch Desdemona and Cassio together, implying that there's something going on between them.
At first Otello is unconcerned. But when Desdemona comes to him and speaks on Cassio's behalf, Otello becomes suspicious, and then angry. When Desdemona offers him her handkerchief Otello doesn't even look at it, and lets it drop to the ground. Emilia quietly picks the handkerchief up, and Iago takes it from her.
Otello dismisses the women and is left alone with Iago, who continues to suggest that Desdemona has been unfaithful. When Otello demands proof, Iago produces Desdemona's handkerchief — saying he got it, the day before, from Cassio. Otello is overcome with anger, and Iago joins him in swearing revenge.
As ACT THREE opens, a herald announces a delegation from Venice, Iago tells Otello to hide himself and wait. Iago says that Cassio will soon appear, along with further proof that he and Desdemona have been having an affair.
Iago leaves, and Desdemona enters. She and Otello sing together, but it's very different from the lyrical, romantic duet they sang in the first act. This time, Otello can barely contain his anger, and his bitter, cryptic comments to Desdemona only confuse her. Finally, he flatly accuses her of infidelity. She's heartbroken by his false suspicions, and responds by praying for him. At first Otello seems placated, but soon he insults her one last time, and pushes her out of the room.
After Otello sings a monologue, pondering his troubles, Iago appears and quickly takes charge. He leads Otello to a place where he can eavesdrop. With Otello listening, Iago goads Cassio into describing a recent dalliance he's had — actually with a courtesan named Bianca. Otello thinks Cassio is describing a night with Desdemona. Iago even gets Cassio to produce Desdemona's handkerchief — which Iago had hidden in Cassio's room.
As trumpets announce the arrival of the Venetian ambassadors, Otello and Iago discuss what method of punishment is appropriate for Desdemona. They agree on a quiet strangulation while she's in bed. Iago slips off to fetch Desdemona, and the Venetian dignitaries make their entrance. Lodovico gives Otello a letter from the Doge, and Otello announces that he must return to Venice. Reluctantly, he'll be leaving Cassio in his place. During this speech, Otello directs a series of angry asides to Desdemona.
Iago then assures Otello that he will deal with Cassio and assigns the task to Roderigo. Otello is still wild with jealousy. He dismisses everyone, and finally lashes out at Desdemona with a curse. Left alone with Iago, Otello mumbles incoherently before fainting. Iago stands over him, gloating in triumph.
ACT FOUR begins with Desdemona in her bedroom, talking with Emilia about Iago's strange and frightening behavior. Desdemona also says she's had premonitions of death. She sings the beautiful "Willow Song," about a girl abandoned by her lover. After saying goodnight to Emilia, Desdemona kneels to pray. She sings a poignant "Ave Maria," and goes to bed.
Otello quietly enters the room. He lays down his sword, approaches the bed, and gently kisses Desdemona. The third time he kisses her, she awakens. The two of them sing together, alternating between tender reminiscences and, on Otello's part, increasingly violent denunciations. Desdemona continues to plead her innocence. The tension builds to the breaking point and Otello strangles his wife.
From outside, Emilia hears the commotion and rushes into the room, saying that Cassio has just killed Roderigo. She finds Desdemona dying, and knows what has happened. Desdemona makes a last attempt at defending Otello, but Emilia sounds an alarm. Iago and a group of armed men rush into the room. Emilia admits that she is the one who actually gave Iago Desdemona's handkerchief — the supposed proof of Desdemona's infidelity. The soldier Lodovico reports that Roderigo, as he lay dying, confessed his own part in Iago's conspiracy, and Iago slips from the room.
Otello finally understands how wrong he has been. He reflects on his past glory, and his love for Desdemona. Then he stabs himself. Dying, Otello drags himself towards Desdemona's body, saying "ancor'un bacio" — "one more kiss" — the words of their blissful love duet from Act One.