Three people traverse the pitch-black St. Marx cemetery on a late autumn evening in 1809: Mozart's widow Constanze Nissen, the researcher Dr. Anton Mesmer and his servant. Mrs. Nissen has promised to show Mozart's grave to Dr. Mesmer in return for an appropriate payment. Overwhelmed by the mystery of the place, Dr. Mesmer reminisces back to a performance given forty years before in his Viennese baroque garden by the child prodigy Amadé.
The music of that occasion sounds again, and we are transported back to Vienna in the year 1768. The Salzburg conductor Leopold Mozart presents his son Wolfgang Amadé to the illustrious Viennese society on an open-air stage. Leopold is assisted by Amadé's older sister Nannerl, who herself was a child prodigy until recently. Amadé is indisposed and cannot perform. The young boy finds a mysterious little box, which he is permitted to keep thanks to an intervening word by the Countess Waldstätten.
Nine years later. The child prodigy Amadé has turned into a young man named Wolfgang. He shows his sister Nannerl a red coat which has ordered custom-tailored. His father Leopold enters and forbids Wolfgang to wear the coat. He demands that Nannerl return the coat and that Wolfgang finish the serenade which his prince in Salzburg has commissioned.
On stage it is not Wolfgang who composes the score, but instead the child prodigy Amadé, who literally embodies Mozart's genius as a second separate individual. This "immortal porcelain child" follows Wolfgang through the entire piece like a shadow, invisible to all other persons. They see only the mortal human Wolfgang Mozart. But the small Amadé, Mozart's unrelenting genius, is always there somewhere. The "wunderkind" composes without interruption, often bent over a stack of music paper, which the adult Wolfgang is playing, drinking, loving or dreaming.
While Amadé composes the serenade, Wolfgang wrenches with the anger he feels towards his father. "When," he asks himself, "will he stop patronizing me? Why can't he accept me as I am?"
Under the supervision of chamberlain Count Arco, the royal servants at the Salzburg court prepare a feast for the evening meal. Archbishop Colloredo appears and admonishes all to hard work and discipline. Wolfgang Mozart arrives late. When he finall comes, accompanied by his father, his arrogance offends the already impatient aristocrat. Colloredo tears apart the score which Mozart gives him and throws it away. Enraged, Wolfgang quits.
Leopold is appalled by Wolfgang's lack of self-control. However, Wolfgang feels a sense of freedom and is certain that he can find a better position in Vienna, Paris or London. He wants to set off on his travels alone. But Leopold knows how dependent on others Wolfgang is, and does not want to let him go.
Wolfgang gets his own way and leaves Salzburg, accompanied by his mother. Nannerl tells the curious market women in Salzburg about her brother's travels. She is certain that Wolfgang will land a prestigious position. Count Arco knows better though: Prince Colloredo will use his influence to thwart Mozart's efforts.
Back in Salzburg, Leopold deeply regrets that he has allowed his son to leave. Dark premonitions haunt him, for he is convinced that the world is an evil place. He hopes that his gullible Wolfgang can protect himself by wrapping his heart in iron.
His fears prove to be justified. In Mannheim, Wolfgang falls into the clutches of the Webers, a family with many daughters and a questionable reputation. The attractive and musically gifted daughter Aloysia is chosen by Madame Weber to woo Wolfgang. She succeeds, and Mozart gives the Webers money. He promises to make Aloysia a prima donna.
When Leopold learns of Wolfgang's relationship with Aloysia Weber, he sees his worst fears realized. In a conversation with God he searches for a way to save his son. He commands Wolfgang to return at once to Paris - accompanied by only his mother. Wolfgang obeys with a heavy heart. To keep from losing Aloysia, he sends the Weber family all his money from Paris, including that which his father had sent from Salzburg. As a result, he and his mother live in poverty. His mother dies in a wretched room. In despair, Wolfgang questions the meaning of life.
He returns to Salzburg alone, an utter failure. The envious servants of the archbishop deride Wolfgang Mozart's return to Salzburg, re-creating his humiliation with glee. The theater direction Emanuel Schikaneder, whose troupe is making a guest appearance in the town, is delighted at the theatrical bent shown by the crowd in the tavern.
Leopold Mozart believes he has a way to hold Wolfgang by him: he presents his son a list of the debts which can be paid back only through work. Countess Waldstätten pays a visit and offers to take Wolfgang to Vienna. Leopold curtly declines: Wolfgang must stay in Salzburg.
A few months later another opportunity arises. Archbishop Colloredo is travelling with his court from Salzburg to Vienna and orders that Wolfgang go there too. Count Arco is however against this plan. He fears that Wolfgang could elude the prince in Vienna.
But Mozart remains in Colloredo's entourage. Soon he sees an exhibition in the Vienna Prater. It turns out that the show he is watching is presented by the Weber family, which has moved its activities from Mannheim to Vienna. Wolfgang again loses his head. Aloysia has meanwhlie married another man, but Wolfgang discovers that he is infatuated with the daughter Constanze Weber. He is persuaded by Cäcilia Weber to move into the family's apartment.
Word of this gets back to Salzburg. Leopold Mozart senses that his son will stay in Vienna. Betrayed and bitter, he hurls memorabilia from the "wunderkind days" into the Salzach river. Nannerl attempts in vain to console her father. She remains alone and realizes that her own childhood dreams cannot be fulfilled. While Wolfgang will follow the path determined by his state of genius, she is bound by her sense of duty to her father, and by the predetermined role of a woman in a bourgeois society.
Trouble brews in Vienna. Archbishop Colloredo breaks his promise to present Wolfgang to the Emperor. Instead, he prematurely orders him back to Salzburg. Mozart is furious and argues with the prince. The conflict escalates and ends with Mozart's dismissal. Count Arco literally kicks the rebellious composer out of the Archbishop's quarters.
Wolfgang has scarcely begun to enjoy his newly-won freedom, when he realizes that he is not really free at all. His genius, which continually follows him in the form of the porcelain child Amadé, places greater demands on him than any of his sponsors or superiors had ever done. Amadé has become a demon, and Wolfgang is damned to serve him.
Dr. Mesmer's servant begins to dig at the gravesite in St. Marx cemetery. Constanze Nissen refuses to answer Dr. Mesmer's indiscrete questions about Wolfgang's "strange ways". She avoids questions about the years she was married to the deceased. Dr. Mesmer remembers that Mozart sometimes behaved very peculiarly.
We are transported back to the year 1781. Following a Mozart concert, his supporters and detractors debat the importance of the composer. They agree on one point: in Vienna, it isn't enough to be talented and successful. One must also excel in the art of the intrigue.
Wolfgang has moved out of the Weber's apartment. Nonetheless, his love for Constanze is stronger than ever. She visits him one evening. Constanze has left the family house and turns now to the only person whom she trusts. When Wolfgang takes her into his arms, Cäcilia Weber and her new partner Johann Thorwart stand in the door. They accuse Mozart of seducing her daughter and they force him to sign a contract which requires Wolfgang to either marry their daughter or to pay her lifelong expenses. Constanze is outraged at her mother's plot. She secretly absconds with the contract and tears it apart in front of Wolfgang.
Troubled feelings remain. In a nightmare, Wolfgang Mozart sees himself pursued by the figures of his own life. He finds himself suddenly at a masked ball, where no one is whom he seems to be. Wolfgang searches for the answer of his life. His masked father seems to know, but he disappears in the confusion of the masks. The countess demands of Wolfgang that he stop following his father around. He should finally grow up and be an adult.
Back in Salzburg, Nannerl has fallen in love with a destitute man whom Leopold disappoves of. She can only marry him if she can provide a dowry. She asks her brother to give back the money which their father had originally set aside for her, but had sent to Wolfgang when he was in Paris. Wolfgang has the money and is ready to give it to her. He carries the money in an envelope and plans to send it to her in the mail. False friends ply him with liquor and cheat him of the money in a card game.
Constanze is not the woman who can cure Mozart of his weaknesses. She loves life too much to correct his frivolity. After a wild night on the town she goes through the rumpled Mozart apartment. She adores the carefree life her husband leads. Recovering from a hangover, she thinks back on the exciting evening. Her maxim is: it would truly be a shame to pass up a dance.
Vastly successful, Mozart can afford a life of luxury. The only thing standing in the way of perfect happiness is a reconciliation with his father. Following years of estrangement, Leopold returns to Vienna to see his son. Through her father's letters, Nannerl in Salzburg reads the news of his visit. Leopold is initially enthusiastic, for Wolfgang shows daily that he has become successful, well-off and respected in Vienna. However, when Leopold realizes that he has become superfluous to his son, his mood darkens. Wolfgang seeks reconciliation with his father, but in vain. He gives him the mysterious box that has accompanied him since childhood. Leopold opens it. It is filled with money that would allow Mozart's father to quit his detested duties to the Archbishop. However, Leopold misunderstands the present. "What you owe me, you can't pay for with money!" he shouts, and throws the box and its contents at Wolfgang's feet.
Leopold runs off, and Wolfgang is unable to catch up with him. He cannot comprehend why his father misunderstands him, and without the approval of his father, he can't enjoy his success. Yet as an artist he has to go his own way - there is no other choice. Deeply upset by this final separation from his beloved father, Wolfgang slips into a condition of mental confusion. His genius Amadé grasps this moment of weakness and attacks Wolfgang. In fact, Amadé has been displeased with Wolfgang's attitude for some time now.
Archbishop Colloredo in Salzburg has not forgotten his former favoured court musician. Amazed, he pores over a music score of Mozart's. He summons Loepold to learn if the father has relayed to his son the offer of a new position at the court. Leopold advises the archbishop to forget Wolfgang. He promises to produce another child prodity and is promptly dismissed. Alone, Colloredo quarrels with God. For such an enlightened man, it is difficult to accept the possibility that reason and order can be bested by something as unexplainable as the magic of music.
Wolfgang learns that the patrons of his first concert were right: in Vienna, it is not enough to be talented and successful. His star sinks. Nonetheless, he continues to be paid well. But the money he earns always mysteriously disappears. Cäcilia Weber takes more and more of Mozart's earnings. She demands that he beg to friends and patrons for money. Wolfgang slowly matures during this humiliating situation. When he finally revolts against the Webers' wishes, the news arrives from Salzburg that his father has died.
Wolfgang bids farewell to his father in St. Stephan's Cathedral. What he says is an accusation rather than a lament. He knows that Leopold has suffered at least as much as he has. Wolfgang realizes bitterly: "God's miracles are not for free." While leaving the cathedral, a masked man approaches him. He gives Wolfgang the commission to compose a requiem.
The news of the French Revolution reaches Vienna on an evening in July 1789. An agitated crowd debates the events. Wolfgang speaks up when a monarchist defends the emperor as "father of the people", replying that "self-motivated children don't need a father!" Emanuel Schikaneder standing nearby warns him against become agitated. He reminds the composer that artists have more effective means of expressing themselves. In the garden of his theater, Schikaneder gives Wolfgang the libretto to "The Magic Flute", which Amadé takes. The theatre director urges Mozart to write many catchy melodies, for he desperately needs a success. An actress is called to "inspire" Wolfgang. He disappears with her into a garden house. Amadé sits on the roof, composing. Night falls. Figures from "The Magic Flute" waft through the garden.
The premiere of "The Magic Flute" is an overwhelming success. An enthusiastic crowd streams out of the theater. Merchants sell portraits of both the child prodigy and the adult Mozart. Admirers climb onto the roof of the theater. The ovations gradually begin to anticipate the cult of Mozart cherished by later generations.
But Mozart cannot enjoy his newly-won fame. He has the feeling that he has been poisoned. Pale and fevered, he lies in bed, while Amadé sits swinging his legs on the edge of the bed composing the "Requiem". When his inkwell runs dry, he pricks Wolfgang's arm - as he has often done before - in order to keep working, using blood as ink. Wolfgang begs his "doppelgänger" for mercy. Finally Amadé spears his quill directly into Mozart's heart.
Time and space become one. The dead composer is the victim of scavengers and memento hunters. The figures in his life emerge from the darkness and circle the deathbed. Out at the St. Marx cemetery, Dr. Mesmer holds up a human skull. Nannerl finds the mysterious box and opens it. A little melody sounds, reminding her of the "wunderkind" days.