The film of Amadeus starts with an older man whose name was Antonio Salieri. Screaming after cutting his throat confessing he has killed Mozart, Father Vogler asks him to repent. A long narrative begins with Salieri’s childhood and in the film we learn that he is passionate about music. Unfortunately, his father made it impossible for him to follow his dreams as a composer. Salieri’s father dislikes music and mocks his passion for it, as well as his musical idol, the six years old prodigy whose name was Mozart.
Young Salieri turns to God and promises chastity and devotion if God turns him into a legendary musician whose name and work lives on throughout time. Soon after Salieri’s wishes to God, his father dies; he believes that God has accepted his promise. His father’s death allows Salieri to study music in Vienna. After a couple of years Salieri becomes a composer in Emperor Joseph II's court and throughout this time in his life, Salieri keeps his promise to God; he is religious, chaste, and generous to others. Salieri's happy life soon changes when Mozart comes to the city. Salieri meets Mozart at a party that was held by Prince-Archbishop Colloredo of Salzburg. At the party Mozart acts inappropriately with a young woman and ruins Salieri’s thoughts and admiration for him. Although, he still agrees with Emperor Joseph on behalf of his decision to hire Mozart to compose a German opera for the national theater. Salieri soon regrets this decision when Mozart insults one of his pieces and by sleeping with a woman he is in love with, whose name is Katherina Cavalieri.
Mozart becomes a burden on Salieri's relationship with God and he realizes God has not answered his prayers from his teenage years. He realizes that Mozart is one, the most talented and not him. This realization leads Salieri to a dark path. As Salieri turns to the dark side he takes advantage of Mozart's living in Vienna. Mozart only has tutoring positions and his performances as sources of income to support his luxurious lifestyle, which Salieri knows about; this and spreads a rumor that Mozart has inappropriate relationships with pupils. The rumor costs Mozart not only the duty of tutoring Princess Elizabeth, but also the opportunity to tutor other young women in Vienna. Throughout the film Mozart does not realize that a majority of his problems come from Salieri. Instead, he begins to view Salieri as a confidant. Leopold, Mozart's father, comes to Vienna, but isn’t able to do much for Mozart. He had tried to ruin Mozart's relationship with the prince-archbishop. Mozart’s decision to stay in Vienna and to marry Constanze causes Leopold to give up in trying to direct Mozart in a different route. Leopold did not stay long in Vienna for long; he left after arguing with Constanze over Lorl. A young arrives and explains that she has been sent to provide as a housekeeper to the Mozart's household. Constanze soon welcomes Lorl but Leopold is suspicious of her and he turn out to be right about Lorl, she is Salieri's spy. Salieri uses Lorl by having her tell him when Mozart and Constanze are not home. With that said, he used this information to break into Mozart's home.
At Mozart's home, Salieri finds that Mozart is working on an opera based on Pierre Augustin Beaumarchais' play, The Marriage of Figaro. He brings this information to Count Orsini-Rosenberg and Kapellmeister Bonno, who were against Mozart being welcomed to the emperor's court. Count Orsini-Rosenberg and Kapellmeister Bonno then bring the information to the emperor and Mozart is released with the opportunity of continuing the play. After censorship fails, Salieri employs other methods to hurt Mozart's work. Mozart's financial issues begin to take a mental and physical toll on him.
As the film continues, Salieri takes revenge a bit further by wearing a mask and black cape that Leopold once wore to a party. He approaches Mozart and asks him to write a Requiem. Salieri plans on taking credit for the Requiem after he performs it at Mozart's funeral after killing him. Mozart is terrified by the masked figure, but he agrees to do the work since he is in desperate need of money. Mozart feels much more worse in his weak state, although completes The Magic Flute then dies before finishing the Requiem.
During Mozart's death he is not alone. Constanze who had left Mozart comes back with their son, Karl only a few minutes before his passing. The night before Mozart dies he faints in the middle of conducting The Magic Flute. Salieri takes Mozart home to rest, but when Mozart gets home Salieri does not allow him to rest. Salieri insists on Mozart to work on the Requiem by letting him believe that a knock at the door is the masked figure. Salieri volunteers to help Mozart accomplish the feat, Mozart accepts the help then he and Salieri work through the rest of the night. Mozart's funeral is not as grand as one would think, only his family and a few acquaintances attended it and Salieri was one of them. Mozart did not get a tombstone and his body was dumped in a dug out grave. The Requiem was not only unfinished but Constanze dismisses the product and locks it away.
The film ends with old Salieri, the inmates that he sees as the attendant pushes him through a hallway of their mediocrities, the last of it was the sound of Mozart's laugh.