Background and prelude
Spain 1559. Peace has been declared between France and Spain, shortly to be sealed by the marriage of Don Carlos, heir to the Spanish throne, to Elisabeth de Valois, daughter of Henri II of France. They have met, fallen in love, but Carlos's recently widowed father, the King, Philip 11, has decided to marry Elisabeth himself. In the interests of peace she has agreed.
Act I Scene 1
At the monastery of St Just, where Don Carlos's grandfather, Charles V of Spain lies buried, Carlos sings of his love for Elisabeth. His dear friend Rodrigo, the Marquis de Posa, arrives and urges him to join him in fighting the cause of his beloved Flanders, a country oppressed by the Spanish Army. When the King and Queen pass by, Carlos has to be restrained by Rodrigo. The two sing of their mutual friendship.
Act I Scene 2
The ladies of the court enter the garden of the monastery, while awaiting the arrival of the Queen. Thibault, page to Elisabeth, arrives together with the Princess Eboli, who suggests they sing together to while away the time. As the Queen enters, the ladies leave. Rodrigo secretly hands the Queen a letter from Carlos, requesting a meeting. Elisabeth contrives to be alone, and Carlos proclaims his love for her. while she sings of her duty to God and country. King Philip confides to Rodrigo his suspicions about his son and Elisabeth, and orders Rodrigo to watch them.
Act II Scene 1
Having received an anonymous note requesting a meeting, and assuming it to be from Elisabeth, Carlos is shocked to find Eboli, (who is secretly in love with Carlos). On realising that Carlos loves the Queen and not her, as she had hoped, Eboli threatens to disclose all to Philip. Rodrigo arrives and fearing the consequences, persuades Carlos to let him look after any incriminating papers. Carlos reluctantly agrees, and they again sing of their friendship.
Act II Scene 2
Philip's coronation is to marked by an auto da fe, a ceremonial burning of heretics. The people rejoice in the power and might of catholic Spain, as the Flemish heretics are brought on. The ceremony is interrupted by the sudden arrival of Don Carlos with a deputation from Flanders. They plead with the King for clemency for the heretics, but Philip is unmoved. Carlos begs his father to allow him, in preparation for his future role as King, to rule Flanders. Philip refuses. Carlos draws his sword, and only Rodrigo is able to disarm him. The ceremony continues, the heretics are burned and Carlos is unceremoniously removed.
Act III Scene 1
In his bedchamber, the lonely King bemoans his loveless marriage. The Grand Inquisitor reminds him of his duty to the church; Carlos must be executed and Rodrigo handed over to the Inquisition as a heretic. Elisabeth enters, distraught, as she cannot find her jewel case. Philip takes it from his desk and on opening it, the Queen is dismayed to find a picture of Don Carlos. They argue, he accusing her of adultery, she vehemently denying it. Eboli and Rodrigo are summoned. Eboli confesses it was she who planted the picture, and begs for forgiveness. However, when Elisabeth learns that Eboli is her husband's mistress, she is appalled, and sentences Eboli to exile or a nunnery.
Act III Scene 2
Carlos, in prison, is visited by his friend Rodrigo, whose days are also numbered, since the papers he is holding for Carlos have been used as evidence of his own heresy. As he hands Carlos the prison keys, a shot is heard. Falling fatally wounded, Rodrigo tells Carlos that Elisabeth will meet him the next day at the Convent of St Just. Dying, he entreats Carlos to save Flanders. The crowd storm the prison to free Carlos. The Grand Inquisitor terrifies the people into submission.
Carlos and Elisabeth meet for a last farewell, Carlos pledging himself to the cause of Flanders as a tribute to Rodrigo. The King and the Grand Inquisitor arrive to arrest Carlos. In the ensuing scuffle, the ghost of Charles V takes Carlos into the safety of his tomb.