ACT I. France and Spain, c. 1560s. Don Carlo, Infante of Spain, has come secretly to France to see Elisabetta de Valois, to whom he is betrothed but whom he has never met. In the wintry forest of Fontainebleau the two young people meet by chance and fall in love. But when Lerma, the Spanish ambassador, arrives, he tells them that as a condition of the peace treaty between France and Spain, Elisabetta's father has given her not to Carlo but to his father, Filippo.
ACT II. Carlo, in his misery, visits the cloister of the monastery of St. Just, where his grandfather, Carlo V, became a friar and retreated from the cares of the throne. When Carlo confesses to his friend Rodrigo, Marquis of Posa, his love for his father's wife, Rodrigo urges him to devote himself instead to the cause of Flemish independence from Spanish oppression. The two men pledge friendship and devotion to liberty.
Outside the convent, Princess Eboli entertains ladies of the court with a Moorish love song. When the queen arrives, Rodrigo slips her a note from Carlo. She agrees to see Carlo, who reiterates his love for her; when she reminds him that she is now in an impossible position, the distraught Infante rushes off. Filippo, finding Elisabetta unattended, sends her lady-in-waiting into exile. When Rodrigo speaks frankly to the king about his hopes for Flanders, Filippo asks him to watch Carlo and the queen, whom he suspects.
ACT III. Carlo goes to the queen's gardens at midnight to see Elisabetta but instead is met by the masked Eboli, who is in love with him. When he realizes who she is and shows his disappointment, Eboli threatens to bring about his downfall. To protect him, Rodrigo takes incriminating papers from the Infante.
In the square before the cathedral, a crowd gathers to witness an auto-da-fé. Carlo leads a delegation of Flemish deputies to plead for clemency for the heretics. When the king refuses, Carlo raises his sword against his father. To his astonishment, Rodrigo disarms him. As the condemned are led to the stake, a voice from heaven announces the salvation of their souls.
ACT IV. Alone in his study, Filippo laments his wife's indifference. He then calls in the aged Grand Inquisitor, who urges the death penalty for both Carlo and Rodrigo. After the implacable old priest has left, Elisabetta bursts in, crying that her jewel casket has been stolen. The king produces it, and when he forces it open, Carlo's portrait falls out. He accuses his wife of adultery. The queen faints, and Filippo summons Eboli and Rodrigo for help. When the men withdraw, Eboli confesses responsibility for Elisabetta's betrayal - it was she who stole the jewel casket - and when she goes on to confess that she once was the king's mistress, the queen banishes her to a convent. Eboli, cursing her own fatal beauty, vows to save Carlo.
In Carlo's prison cell, Rodrigo explains that he has allowed Carlo's incriminating papers to be found on his person and thus taken the blame for the Flemish insurrection. As he takes his leave, he is shot to death by a soldier of the Inquisition. The Infante is given his freedom by his father as a mob storms into the cell to defy the monarch. Filippo is protected from the throng by the arrival of the Inquisitor.
ACT V. Back in the cloister of St. Just, Elisabetta waits to bid farewell to Carlo. The lovers are surprised by Filippo and the Inquisitor, but the Infante is saved from them when Carlo V emerges from the shadows and draws him into the tomb.
by John W. Freeman
-- courtesy of Opera News