At the church of the Mendicanti in Venice, Consuelo is the most gifted of all the pupils of the famous teacher, Porpora. Consuelo is a poor orphan child, and Porpora makes her his goddaughter. Before the death of her mother, Consuelo promises that she will one day become betrothed to Anzoleto, another poor musician of Venice.

Through the efforts of Anzoleto, Consuelo is engaged as the prima donna at the theater of Count Zustiniani, replacing Corilla, who also was Porpora’s student. Consuelo is a great success, but Anzoleto, who was also engaged in the theater at the insistence of Consuelo, is not much of a musician and is not well received. Anzoleto, afraid that he will be discharged, pretends to be in love with Corilla, thinking that he will be safe if both singers are in love with him. Porpora never liked Anzoleto, and at last he contrives to have Consuelo visit Corilla’s home. When they find Anzoleto there, Consuelo is so hurt that she leaves Venice at once, vowing that she will never set foot on the stage again and renouncing the false Anzoleto forever.

From Venice, Consuelo goes to Bohemia, where she is engaged by Count Rudolstadt as a companion for his niece, Amelia. This young noblewoman is betrothed to young Count Albert Rudolstadt, but she fears him because he seems to be insane. Albert often has visions in which he sees scenes of the past and often imagines himself to be the reincarnated body of some person long dead. When Albert first hears Consuelo sing, he calls her by her name, even though she took another name to hide her unhappy life in Venice. Albert tells Consuelo and the whole family that she is his salvation—that she was sent to remove the curse from him. Consuelo is bewildered.

Albert often disappears for many days at a time; no one knows where he goes. Consuelo follows him but can never find his hiding place until the night she descends into a deep well and finds steps leading to a grotto where Albert and an idiot called Zdenko spend many days together. Zdenko loves Albert more than his own life; when he sees Consuelo coming into the well, he thinks she wants to harm Albert, and he almost kills her. Consuelo escapes from Zdenko and finds Albert. After she speaks soothingly to him, he ceases his mad talk and seems to regain normal behavior. She persuades him to return to his family and not to go back to the grotto without her. Albert tells Consuelo that he loves her and needs her, but, although she no longer loves Anzoleto, she cannot forget how she once loved him, and she asks Albert to wait a while for her answer.

Albert’s father and the rest of the family are grateful to Consuelo for helping restore Albert to his senses. The father, Count Rudolstadt, even tells Consuelo that he will give his consent to a marriage between his son and her, for the old gentleman believes that only Consuelo can keep his son sane. While Consuelo is debating whether she loves Albert and could accept the honor, Anzoleto, deserting Corilla, comes to the castle in search of her. Consuelo slips away from the castle, leaving a note for Albert. She goes to Vienna to rejoin Porpora.

Without funds, Consuelo has great difficulty in reaching Vienna and walks most of the way. In her travels, she meets Joseph Haydn, a young composer who is on his way to the castle to find her; he hopes he can persuade her to take him to Porpora, under whom he wishes to study. Dressed as a peasant boy, Consuelo accompanies Haydn to Vienna. One night they take refuge in the home of a canon of the church. While they are there, Corilla comes to the door, seeking a safe place to give birth to her child. Consuelo has pity on her former enemy and takes Corilla to an inn, where she helps to deliver the child. From a maid, Consuelo learns that Anzoleto is the father. Corilla does not recognize Consuelo, who continues to wear the disguise of a boy.

When Joseph and Consuelo finally reach Vienna, the girl finds Porpora overjoyed to see her again. Haydn becomes Porpora’s pupil, and Consuelo sings for the empress. Then Corilla, who also comes to Vienna and learns that it is Consuelo who befriended her during the birth of her child, arranges for Consuelo to sing in the theater there. Corilla hopes to seal the lips of Consuelo, who knows of the illegitimate child and knows that Corilla abandoned the baby in the home of the canon who gave Consuelo and Joseph shelter. Anzoleto is never heard from again.

Consuelo writes to Albert, telling him that she is almost ready to return to him, but Porpora intercepts the letter and destroys it. Consuelo waits in vain for a reply from Albert. At last, Porpora tells her that he received a letter from the count, saying that he does not wish his son to marry an actress and that Albert concurs in the decision. Consuelo so trusts her godfather that she believes him, not realizing how ambitious Porpora is for her musical career.

Porpora goes with Consuelo to accept a theater engagement in Berlin. On the way, they meet the brother of Count Rudolstadt. Albert asks his father to have someone at a certain place on the road on a specific day and at a specific hour, saying that the messenger is to bring the travelers he will meet there to the castle at once. Albert is very ill, and Consuelo persuades Porpora to allow her to go to Albert. When she arrives at the castle, she learns that his father received a letter from Porpora saying that he will never consent to a marriage between Consuelo and Albert and that Consuelo herself renounced Albert. It was the deathblow. Albert grows very weak and begs Consuelo to marry him before he dies so that his soul can find peace; he still believes that only through Consuelo can he find salvation. The marriage vows are repeated, and Albert, crying that he is now saved, dies in Consuelo’s arms.

Consuelo stays with her husband all night, leaving him only when he is carried to his bier. She then bids Albert’s family good-bye, refusing to accept any of the fortune that is now hers. Then she leaves the castle and goes to join Porpora in Berlin, where Frederick the Great himself worships both her beauty and her art.