The film tells of Liszt's life through surrealistic episodes blending fact, fantasy, and anachronistic elements. At the start, Liszt is caught in bed with Marie d'Agoult by her husband, the Count d'Agoult. The count challenges Liszt to a sabre fight, but Marie begs the count to let her share Liszt's fate. The count's staff traps Liszt and Marie in the body of a piano and leaves it on railroad tracks.
This is shown to be a flashback triggered by the camera-flash of photographers backstage before one of Liszt's concerts. Liszt introduces Richard Wagner to his colleagues, including Gioachino Rossini, Hector Berlioz, Frédéric Chopin, and Hans von Bülow. Liszt pays Wagner to let him perform a variation on a theme from Rienzi. At the concert, Wagner is put off by Liszt's crowd-pleasing showmanship at the expense of serious musicianship, which includes adding the melody of Chopsticks to his Rienzi variation. However, the crowd, consisting largely of young screaming girls, go wild at Liszt's performance, storming the stage. Liszt uses von Bülow to proposition potentially wealthy females in the audience. One is Princess Carolyn, who gives Liszt her address in Russia.
Marie's and Liszt's domestic life is plagued by jealousy over his constant touring and infidelities. They now have three children, the oldest being Cosima. Domestic life has strained Liszt's creativity. Liszt prepares to depart to St. Petersburg to play for the Tsar. Marie threatens to abandon him if he goes. Liszt tells Cosima that he would sell his soul to the devil to compose brilliant music again. Cosima says she will pray to God every day, so that Liszt will meet the devil and sell his soul to him.
Carolyn seduces him, offering him the ability to compose brilliant music in exchange for total control of his life. In an ostentatious scene, Liszt hallucinates a dance sequence with the women of Carolyn's court while Carolyn sinisterly observes from afar. The women then drag Liszt and his oversized erection to a guillotine: Carolyn reveals that the bargain for Liszt's newfound musical prolificacy is the forfeiture of his libertinism.
Next, Liszt, in Dresden during the May Uprising, is conflicted about not supporting his friends in the revolt and spending all his time isolated to compose music (it is heavily implied that Marie and his two youngest children have been killed). Wagner asks Liszt for money so he can escape the country with his family. Wagner drugs Liszt and reveals himself to be a vampire with a mission to write music inspiring a new German nationalism. He sucks Liszt's blood and composes on the piano. Before departing, Wagner leaves him his latest political pamphlet, a Superman comic (a play on Friedrich Nietzsche's Superman).
Liszt and Carolyn travel to the Vatican to get married after the Pope agrees to grant her a divorce from her husband. The wedding ultimately is voided by the intervention of her husband and the Tsar. A furious Carolyn threatens to write an anthology on her disagreements with the church (Causes intérieures de la faiblesse extérieure de l'Église en 1870). Liszt joins the church as an abbé.
The Pope tells Liszt that Wagner has married Cosima and leads a devilish cult organized around his music. He orders Liszt to exorcize him and return him to the Christian faith or else Liszt will be excommunicated and his music banned.
Liszt travels to Wagner's castle, where Wagner and Cosima perform a secret Nazi ritual dressed in Superman costumes. Liszt confronts Wagner, who built a mechanical Viking Siegfried to rid the country of Jews. Wagner reveals himself to Liszt as a vampire and threatens to steal his music so that Wagner's Viking can live. Liszt plays music to exorcise Wagner. Cosima imprisons Liszt and resurrects Wagner in a Nazi ceremony as a Frankenstein-Hitler wielding a machine-gun guitar. Cosima leads the Wagner-Hitler to gun down the town's Jews and kills Liszt with a voodoo doll.
In Heaven, Liszt is reunited with the women he romanced in his life and Cosima, who live in harmony. Liszt and the women fly to Earth in a spaceship to destroy Wagner-Hitler. Liszt sings that he has found "peace at last".