Salieri complains about the decline in the quality of composing and music appreciation. Then he speaks directly to the audience, explaining that he is going to die soon and is not looking for forgiveness for his actions. Salieri adds, “I was a good man, as the world calls good. What use was it to me? Goodness could not make me a good composer. Was Mozart good? Goodness is nothing in the furnace of art” (58). He returns to the night that Constanze brought him Mozart’s compositions. Constanze returned to Salieri shortly after leaving. Mozart has gone to a party without her and she is prepared to give in to Salieri’s advances. Instead, Salieri tells her to take the portfolio and leave. She attacks him, he throws her to the ground, and she leaves. The next day, Salieri takes Katherina Cavalieri as his mistress. Additionally, he resigns from his committees that exist “to help the lot of poor musicians” (60). Finally, Salieri says, “I went to the emperor and recommended a man of no talent whatever to instruct the Princess Elizabeth” (60). The scene cuts to the palace, where Emperor Joseph is surprised to hear that Salieri is not recommending Mozart. Salieri insinuates that Mozart cannot be trusted with the virtue of a young woman he is teaching, and Emperor Joseph agrees since Princess Elizabeth is hardly a musical prodigy anyways.

When the emperor announces the hire, Salieri commiserates with Mozart, who complains that his father will certainly lecture him for failing to secure the job. The Venticelli enter and gossip about Mozart, who still has very few students and now a child to support. Salieri notes that not only did God not punish him for his actions, but he thrived, becoming much more popular and well-regarded than Mozart as a composer. Although Mozart is still producing excellent compositions, he is not attracting audiences. Salieri begins to believe that the accolades about his music are true and starts to live more extravagantly. The Venticelli talk about Mozart, who upon hearing one of Salieri’s latest operas, commented bitterly that Salieri “should be made to clean up [his] own mess” (64). Salieri is offended to learn that Mozart wishes to write an Italian opera, which is Salieri’s specialty. Baron Van Swieten enters to rant about Mozart’s desire to adapt The Marriage of Figaro, a play by Beaumarchais that he regards as “disgraceful” and “a vulgar farce” (64).

Mozart enters and explains that he wants to write “a piece about real people” (64), to the horror of Van Swieten and Von Strack. Van Swieten lectures, “Opera is here to ennoble us, Mozart—you and me just as well as the Emperor!” (65). Mozart disagrees, exclaiming that opera is “realer than any play! A dramatic poet would have to put all those thoughts down one after another to represent this second of time. The composer can put them all down at once—and still make us hear each one of them” (66). Mozart describes the job of composers as interpreting individual voices and turning them into something that sounds like “how God hears the world” (66). Amused, Van Swieten advises Mozart to “be more serious with [his] gifts” (66). Before exiting, Mozart asks the Barons to tell the Emperor that he has finished the opera and only needs to write it down. Once Mozart leaves, Von Strack explodes, calling him “intolerable” (67). Salieri wonders how he can put a halt to The Marriage of Figaro. Orsini-Rosenberg enters to inform the men that Mozart has finished the opera, and they begin to plot in Italian as to how they might stop the opera. Von Strack demands to know what they’ve said, and Orsini-Rosenberg tells him, “Just wait and see!” (68).

At the theatre, Orsini-Rosenberg waits as Mozart enters with his newest score. Orsini-Rosenberg informs Mozart that the Emperor has banned ballets in his operas. Mozart argues that the dance in his piece is integral to the story, and not a ballet, but Orsini-Rosenberg remains firm and rips the offending pages out of the score. Mozart protests that this will ruin the climax of the opera, and suddenly blames Salieri for this turn of events. Orsini-Rosenberg calls this accusation “absurd” (69) and suggests that Mozart rewrite, since he is known for writing quickly. Mozart insists that he does not rewrite when “the music’s perfect” (69) and wants to speak to the emperor, but Orsini-Rosenberg tells him to either rewrite or “withdraw the opera” (70). Irate, Mozart insults him as he leaves. Salieri enters, and offers to intercede and speak to the emperor about attending a rehearsal. Mozart is surprised at this generous offer, but when Salieri exits, he informs the audience that he did not actually speak to the emperor.

Regardless, “[e]ntirely against his usual practice, the Emperor appeared” (71) and attended a rehearsal. Salieri is flummoxed as Mozart thanks him profusely. The Emperor enters the rehearsal just at the moment when the dance would occur and watches, confused, as the scene proceeds in silence. Emperor Joseph is surprised to learn that the dance was cut to comply with his rules, and tells him to put the music back in. At opening night of Figaro, the audience is appreciative. Salieri knows that this opera is brilliant and will endure. But at the end, Salieri is gratified to see that the Emperor is yawning. Emperor Joseph calls the opera “most ingenious” (74) but complains that it was too long, to Mozart’s dismay. Mozart asks Salieri for his opinion and Salieri confesses, “I think the piece is… extraordinary. I think it is… marvelous” (75). Mozart replies, “I’ll tell you what it is. It’s the best opera yet written. That’s what it is. And only I could have done it. No one else living!” (75). Mozart exits, and the Venticelli gossip that Orsini-Rosenberg is furious. Salieri explains that in the end, he did manage to get the opera cancelled and it only played nine times. Salieri wonders if God is even paying attention to what he is doing.

In the Waldstädten Library, Mozart is telling Salieri that he is considering moving to England where he might be appreciated. Salieri encourages him, and Mozart confides that he can’t afford to relocate, and his father has refused to help. Mozart angrily insults his father and is shocked when the Venticelli enter and announce that his father has died. Mozart expresses guilt at the ways he spoke against his father and acted against his wishes. In response, Salieri opens his arms to embrace the younger composer and Mozart gratefully calls him “Papa!” (78). Salieri tells the audience that Mozart’s father inspired the role of the Ghost Father in Mozart’s opera Don Giovanni. Salieri reflects that he could have stopped waging war on Mozart and shown some pity, but he was angry that God would not inspire him to write music that was just as good. Salieri resolves to “reduce the man to destitution. Starve the God out” (78). In the Palace of Schönbrunn, Mozart tells Salieri that he’s broke. Emperor Joseph tells Salieri that they need to find the composer a job. The Emperor mentions that the position of Chamber Composer is open because Gluck has died. Salieri is shocked at the suggestion that Mozart take Gluck’s job and proposes that he offer the position but pay far less than his predecessor received. The Emperor agrees.

Mozart, having received the offer, is offended. Salieri tells him that he suggested Mozart for the position, and Mozart immediately changes his attitude, thanking Salieri and apologizing. Mozart laughs and immediately doubles over in pain, confessing that he often has stomach cramps. After Mozart exits, Salieri gloats about having “ruined Mozart’s career at Court” (80). Salieri adds that God rewarded him for this when the Venticelli enter to tell him that Kapellmeister Bonno has died and the Emperor has appointed Salieri to his position as the “First Royal and Imperial Kapellmeister to the Court” (81). The Venticelli note that Mozart looks terrible and is constantly taking medication. Outside, in a park, Salieri and the Venticelli meet Mozart walking with a noticeably pregnant Constanze. They are dressed in poor clothing. Mozart congratulates Salieri, and Salieri offers sympathy for Mozart’s ailing health and frightening bad dreams about a sinister figure. After the Mozarts exit, the Venticelli gossip that Mozart is unable to earn enough money and has resorted to begging from the Masons, a fraternal order, and its members are preventing Mozart from starving.

At the Masonic lodge, Baron Van Swieten approaches Mozart and admonishes him for using the order to beg for money. Van Swieten suggests that Mozart give concerts, but Mozart admits that he is “no longer fashionable” (84). Van Swieten offers him a meager job making an arrangement of Bach’s music, and Mozart bitterly agrees. However, Mozart tells Salieri that he has been approached by another Mason to write a vaudeville piece about brotherly love and receive half of the ticket money as payment. Salieri jokes that Mozart ought to write about the Masons, and Mozart takes the suggestion seriously even though Salieri warns that their rituals are secret. Salieri agrees that Mozart can adapt the rituals, knowing that this will ruin his reputation with the Masons. They agree to keep this opera secret until it is finished. The Venticelli are abuzz talking about the secret opera, but Salieri gleefully tells the audience that Mozart’s opera is exposing the secrets of the Masons and will destroy him.

At home, Mozart and Constanze are freezing as Mozart tries to write. Mozart tells Constanze that his father was right when he predicted that the couple would end up as beggars. To Mozart’s surprise, Constanze tells Mozart that she hated his father, and Mozart calls her “silly” (86). Constanze informs him that the fire they were warmed by the previous night was made up of his father’s letters, most of which were insulting Constanze. Mozart is furious, but Constanze isn’t sorry and mocks him until Mozart begs her to stop. Mozart admits, “I’m frightened, Stanzi. Something awful’s happening to me” (87). He talks about the sinister figure in his dreams and Constanze threatens to leave him if he continues. He apologizes, and they begin their baby-talk flirting until suddenly she cries out in pain, having gone into labor. The Venticelli express pity of their new child, a boy, born to a poor family with “the father a baby himself” (89). Then Mozart tells Salieri that Constanze has left, declaring him insane after he admitted that the sinister figure in his dream told him to write a Requiem Mass, although there is no one who has died to whom to dedicate it. Salieri promises to attend his vaudeville opera and to bring Katherina Cavalieri.

Salieri describes the opening of the opera, The Magic Flute at “a crowded music-hall—in a tenement” (91). Mozart looks ill. Salieri raves about the profundity of the opera, but Mozart is surprised to see Baron Van Swieten in attendance as Van Swieten attacks him for representing the Masons and their secret rituals onstage. Van Swieten tells Mozart not to speak to him again, and Mozart’s social standing is effectively ruined. In the end, he did not even receive the payment he was promised for the opera. The Venticelli describe Mozart, who now sits and all day, “[w]riting—like a man possessed” (94). They wonder what Mozart is working on, but Salieri knows that he is “writing his Requiem—for himself!” (94). Salieri confesses his cruelest trick yet. He dressed as the sinister man that Mozart has seen in his dreams. For a week, Salieri walked past Mozart’s window in this costume and showed him on his fingers the number of days Mozart had remaining to finish writing.

On the seventh night, instead of showing his fingers, Salieri beckons him with his hands. Mozart invites him in, begging for more time as the mass is not finished. Salieri, seeing the music that he has written, admits that it is good. Salieri “tears off a corner of the music paper, elevates it in the manner of the Communion service, places it on his tongue and eats it” (96). Then, Salieri says, “I eat what God gives me. Dose after does. For all of life. His poison. We are both poisoned, Amadeus. I with you: you with me” (96). Horrified, Mozart removes Salieri’s mask. Distraught, Mozart cries out to God. Salieri tells him that God does not love him (or anyone) and begs Mozart to just die. Like a child, Mozart calls Salieri “papa” (97) and sings a nursery rhyme. When Constanze returns, he tells her, “Salieri… Salieri has killed me” (98). She comforts the dying and crazed Mozart, telling him, “No one has hurt you” (99) as the Requiem plays. Constanze pleads with him to get well, but he dies. She screams silently and the final chord of the Requiem does not resolve. Mourners, dressed in black, enter. Salieri explains that Mozart’s official cause of death was “kidney failure, hastened by exposure to cold” (100). Mozart receives a pauper’s burial.

Salieri admits that he felt relief, “and pity too, for the man I helped to destroy” (100). Eventually, Constanze marries again but moved to Salzburg, “birthplace of the Composer, to become the pious Keeper of his Shrine” (100) and speaks kindly of her late husband. Salieri discovers that the sinister figure was never in Mozart’s imagination. In fact, he was sent by “a certain bizarre nobleman called Count Walsegg” (100) who hoped that he could take the work from Mozart and “pass it off as his own” (101). In fact, he succeeded, and the Salieri conducted the Requiem as Count Walsegg’s Requiem. Salieri says that God finally punished him, as he became famous and then lost it all, only to die in obscurity. Salieri is, once again, an old man. Morning has arrived and it is time for him to die, confessing falsely to having murdered Mozart with arsenic. If he can’t be remembered as a great composer, he will live on in infamy as the man who killed one. A servant brings Salieri a razor, and Salieri cuts his own throat. But according to the Venticelli, he doesn’t die. And in the end, no one believes his confession that he killed Mozart. At the end of the play, Mozart’s music is heard throughout the theatre.