ACT I: Dawn in the cloister of the monastery of San Yuste in Spain.
The tomb of Charles V is visible with a lone monk praying before it. The voices
of other monks come from the chapel, singing of the dead Emperor and praying
for his soul. The monk comments on Charles's ambition to rule the whole world,
and he is now only silent dust.
As the monks file across the cloister, an agitated Don Carlo enters, thinking of Elisabetta whom he thinks was stolen from him by his father King Philip. He also fondly remembers their meeting at Fontainebleau (Io l'ho perduta — I have lost her). He thinks he hears the voice of his grandfather, Charles V who has been appearing as a ghost in the cloister.
Rodrigo (Posa) enters and begs the prince to help the people of Flanders (The Netherlands). When asked why he is so sad. Carlo confesses his love for Elisabetta. A shocked Rodrigo responds, "Your mother!", and advises him to ask his father to allow him go to Flanders where he can help the oppressed people, forget his sorrow and find a meaning for his life. Together they swear to live and die together (Dio, che nell'alma infondere — God, who [wished] to instill in our souls). To the sound of their duet and the chant of the monks, Philip enters with Elisabetta, who starts when she sees Carlo, and kneels before the tomb. Note: the last word of the scene is Libertà.
ACT I Scene 2: A garden at the gates of San Yuste.
The ladies of the court and the page, Tebaldo, are singing around the fountain.
Princess Eboli asks them to join her in a song while they wait for the Queen,
and she sings of a Moorish king and a veiled woman. As they finish, a sorrowful
Queen appears, followed shortly by Rodrigo. Under the pretense of handing her
a letter from her mother, Catherine di Medici of France, he slips her a note
from Carlo. As Rodrigo and Eboli gossip about France, Elisabetta hesitantly
opens the note, fearful of betraying her feelings. In the letter Carlo asks
her to trust Rodrigo who then begs the Queen to see Carlo once more. Eboli wonders
if Carlo is in love with her. Elisabetta sends Tebaldo to summon Carlo,
and when he arrives, the others leave them alone.
Carlo begs Elisabetta to intercede for him with the King to allow him to go to Flanders. When she promises to try, he cries out at her seeming indifference to his leaving. She tells him to respect her honor but confesses that she would believe herself in heaven if she could only live with him. However, when he cries out that he loves her and tries to embrace her, she recoils in horror. He flees, just as Tebaldo announces the arrival of the King, who angrily demands to know why the Queen has been left alone and dismisses the lady-in waiting, the Countess Aremberg, who should have been attending her. The Countess is to return to France, and a tearful Elisabetta comforts, her giving her a ring to take back with her (Non, pianger, mia compagna — Don't cry, my companion). All leave except Philip who calls Rodrigo back. Why had he not sought an audience with him to receive his thanks for his loyal service? Rodrigo does not want a material reward for himself; he merely wants to serve Spain. He does beg for mercy for the suffering Flemings, but Philip asserts that only the sword can rule that people. That is how he has controlled Spain and made it peaceful. In vain, Rodrigo continues to plead; but the King is implacable. He does however warn Rodrigo to "beware the Grand Inquisitor". He then confesses that he is suspicious of the Queen and his son. He trusts Rodrigo, who kneels and kisses his hand, as the only man allowed free access to the Queen so that he can search the hearts of those he suspects.
ACT II Scene 1: The Queen's garden
Carlo reads a note which he thinks is from Elisabetta and sings of his love
for her. A masked woman, Eboli, arrives, but Carlo thinks she is Elisabetta
and pours out his heart to her. When she ardently responds and removes her mask,
he discovers his mistake. She questions his sudden coolness and warns him that
disaster awaits him. She has overheard Rodrigo and the King speaking of him
in grim tones and offers to save him. When he refuses, she realizes he thought
she was the Queen. Rodrigo enters, and she tells him she will seek revenge against
Carlo; his fate rests in her hands. However, Rodrigo asserts that God will protect
the innocent and draws a sword on her. Carlo stops him. Rodrigo warns Eboli
to keep silent about what she knows. Once more warning Carlo to beware, she
leaves. Rodrigo asks the prince for any secret papers he may have on him. At
first Carlo does not want to trust him but finally gives him the papers.
Scene 2: A large square in Madrid in front of the church
of Our Lady of Atocha
Music summons all to attend the auto-da-fe and a vast crowd assembles.
Monks lead the condemned across the square, and the royal procession forms before
the church. A herald signals the opening of the church doors. As Philip boasts
of his vow to kill the wicked, Carlo brings a delegation of Flemings to kneel
before the King and beg for mercy for their countrymen (Sire, no, l'ora estrema
— Sire, no, the last hour). Although the crowd also begs Philip to have
mercy on the Flemings, he orders the guards to take them away. Carlo demands
his father give him Brabant and Flanders and draws his sword in defense of the
petitioners. When Philip orders his son disarmed, Rodrigo takes his sword and
gives it to the King. In thanks, Philip dubs Rodrigo a Duke. The funeral pyre
is lit as the crowd sings the praises of the king, the deputies bemoan the sight,
and a voice from heaven prays for the souls of those who will die.
ACT III Scene 1: The King's study in Madrid
Alone, the king meditates on his torment in learning that Elisabetta never loved
him (Ella giammai m'amo — She never loved me). The Count di Lerma
announces the old, blind Grand Inquisitor. Philip tells him that his son Carlo
is in rebellion against him and asks his advice. Should he let him escape or
kill him? If the latter, will the Inquisitor absolve him? The Inquisitor tells
him the good of the kingdom is worth a life; God sacrificed his own son for
the good of the world. He then warns him of Rodrigo and demands the King also
give him to the Inquisition. Philip refuses and, after the Inquisitor leaves,
remarks that the throne must always bow to the altar.
Scene 2: Carlo's prison.
Rodrigo has come to say farewell. He will die but Carlo
must escape and flee to Flanders (O mio Carlo). Carlo's papers were found
in his possession and have identified him as the leader of the revolt in Flanders.
When assassins in the garb of inquisitors appear and shoot him, he says his
farewell (Io morrò — I shall die). His dying words are, "Save
Flanders!". Philip arrives and tries to return his son's sword, but Carlo repulses
him. As Philip cries, "Who will restore that man [Rodrigo] to me?", an alarm
sounds. The people have risen and demand the release of Carlo, not knowing his
father has already freed him. A disguised Eboli is with them. The Inquisitor
arrives and orders the crowd to kneel before the king. The curtain falls as
they comply.
ACT IV: The cloister of San Yuste.
Elisabetta kneels before the tomb of Charles V and begs him to intercede for
her with God. (Tu, che la vanità — You [who knew] the vanity
[of the world]). She recalls the happy days at Fontainebleau. Carlo is coming,
but he must leave her. She herself is reaching the end of her life and will
soon know the peace of the grave. Carlo appears, and they speak of Rodrigo's
sacrifice. Carlo will go to help the people of Flanders and Elisabetta urges
him to do so. Tearfully they say their goodbyes, hoping to meet in heaven (Ma,
lassù ci vedremo — But, up there we will see each other). Philip
and the Inquisitor arrive. Philip seizes Elisabetta and tells the Inquisitor
to take his son. Drawing his sword and defending himself, Carlo backs toward
the tomb which opens revealing Charles V, no longer disguised as a monk. He
emerges and drags Carlo into the tomb with him.