Father, the King of Spain, marries son’s sweetheart for political reasons. Meanwhile, TitleCharacter aims to become Governor of Flanders, but daddy has other ideas. Son nearly stabs father and is put behind bars. He doesn’t take the hint even after the shooting of his amigo, probably a political instigator, and intrigue against his father’s ex-sweetheart, and might wind up in trouble if his dead grandfather doesn’t show up to help.
1559. The Forest of Fontainebleau on the day of the conclusion of the peace treaty between Spain and France. Without the knowledge of his father, King Philip II, the Spanish infante Don Carlos has traveled incognito to the Forest of Fontainebleau to have a look at his betrothed, Elizabeth of Valois, who is to be wed to him as part of the peace settlement.
Carlos succeeds in meeting the French princess, who escorts him to the nearby castle. Without revealing his identity, only his nationality, Carlos strikes up a conversation with the lady, and Elisabeth informs him that that her upcoming wedding has filled her with both hope and anxiety, as it will require her to leave both her father and her home. She asks the Spanish stranger for information about her fiancé: will the heir to the throne really love her? The man assures her that the infante will surely love her until the end of his days and presents her with a jewel casket which conceals a portrait of Carlos. Opening the chest, Elisabeth is delighted to discover that her betrothed is none other than the kind stranger standing in front of her. They declare their love and vow fidelity until death to each other.
Suddenly, the report of a cannon breaks the silence of the forest, and the castle is engulfed in light: news has arrived that the peace treaty has been concluded. Carlos and Elisabeth happily gaze into each other's eyes: their love can at last be sealed in marriage. The Spanish emissary, the Count of Lerma, returns together with Elisabeth's entourage, led by the Countess of Aremberg, the princess' childhood friend. As a sign of his loyalty, Elisabeth's page Tebaldo kisses the hem of the dress worn by the new Queen of Spain and joyfully exclaims: "Long live the Queen, wife of King Philip II!" Elisabeth and Carlos receive the news in shock: "Our condemned souls will never know happiness or peace." The Count of Lerma places the decision in Elisabeth's hands: if she is willing to accept the Spanish king as her husband, then the war will be at an end. The long-suffering women present plead for peace. Elisabeth stammers out a "yes". Carlos and Elisabeth stand broken amidst the rejoicing crowd: they have gone from being an engaged couple to stepmother and stepson.
The monastery of Saint-Just. The grave of Charles V. Dawn.Monks pray for God's mercy on of the soul of the deceased King Charles V, who in his pride had attempted to rule the world. The sound of a bell summons them away.
Carlos enters the empty hall. He has attempted to find solace for his aching heart in the monastery. A monk suddenly addresses the tormented infante: "the sorrowful heart finds peace in heaven." The ghost-like figure departs, leaving Carlos standing in horror: he thinks he recognised the monk as his grandfather, the dead Charles V.
The Marquis of Posa arrives from Flanders after a long period of separation from his friend Carlos. He asks the infante's assistance to rush to liberate the oppressed Flemish, whom the king's troops are massacring: the blood of innocent people is being unjustly spilled! The marquis notices the lethargic state that Carlos is in, and the infante admits to his friend what is tormenting him: he is secretly and hopelessly in love with his stepmother, Elisabeth. Posa asks Carlos to obtain his father's consent to leave for Flanders and become the king of the oppressed. Carlos agrees: the two freedom-fighters take an oath of fraternity together.
The king and queen enter, accompanied by the monks. Don Carlos quakes in the presence of the queen...
Elisabeth's ladies-in-waiting enjoy the beauty of the garden inside the gates of the monastery. In order to pass the time, Princess Eboli, who is secretly in love with Carlos – sings a song about a veiled woman who has captured the Moorish king's heart. At the end of the song, the sombre Elisabeth enters, and the Marquis of Posa is led before the queen. He has brought a letter from Paris, and along with the letter, he slips another message into the queen's hands. It reads: "Trust in Posa as you would trust in me. - Carlos". Posa asks her to grant an audience to her stepson, who is being consumed by some unknown grief. After some hesitation, she agrees to receive Carlos. Posa withdraws with Eboli, and the ladies-in-waiting and pages also proceed out; only the Countess of Aremberg remains in the garden.
Carlos arrives before the queen. The two can scarcely look each other in the eyes. Elisabeth even sends away the Countess of Aremberg, who under the rules of the Spanish court should never leave the queen alone. Carlos asks for Elisabeth to intercede with his father to allow him to depart for Flanders, since the air in Spain is suffocating for him. The queen politely promises her stepson that she will speak with the king on his behalf. The infante breaks down: it anguishes him that Elisabeth behaves so neutrally with him, and that his intention to voyage off elicits no emotions from the woman. Elisabeth asks Carlos to try to understand her situation; the farewell pains her just as much as does him. Hearing this, Carlos enters into a state of euphoria and briefly loses consciousness, and when he comes to, he imagines that he and Elisabeth can be together again. The alarmed queen frees herself from Carlos's embrace. The infante returns to his senses at once and rushes off. The king, Posa and the entire retinue march into the garden. Philip is shocked to find his wife alone and immediately dismisses the Countess of Aremberg from the court. Elisabeth gently bids farewell to her lady-in-waiting. The king and entourage depart.
The Marquis of Posa makes to follow the crowd, but the king stops him. Philip is curious why the marquis didn't ask for an audience, as his services in Flanders would have earned him the king's favour. Posa boldly asks for Flanders to be liberated, but Philip will hear nothing about loosening his grip on the rebellious reformers and hints at threats of the inquisition as punishment for the marquis' audacity. Nevertheless, impressed with Posa's boldness, he thinks better of this and instead orders him to bring his jealous heart either proof or a refutation of his suspicions about his son and wife.
In the queen's garden. Preparations for festivities. Midnight. Carlos arrives, following the instructions ("At midnight, in the queen's garden...") received in an anonymous message that he believes is from the queen. He joyfully awaits his beloved. Draped in the queen's veil, Eboli emerges. Carlos mistakenly declares his love for her. Eboli unveils herself, astonishing Carlos. The princess warns the infante that the king and Posa often whisper about him... Eboli's wish is to protect her beloved. Carlos, however, gently rebuffs the advance, at which point Eboli realises the man's secret: he's in love with someone else!
Rodrigo arrives and attempts to get Eboli to say what she's found out from Carlos. "Do not believe this madman." It is too late: Eboli's heart has been wounded and she seeks vengeance: Carlo's fate is in her hands. The trembling infante realises that he has unwittingly brought trouble to Elisabeth... Posa threatens Eboli, but the woman is undaunted, and if the king's favourite attempts to stand in her way, then she still has her own means to achieve her aim. In impotent rage, Posa draws a dagger, but Carlos restrains him. Eboli departs, swearing revenge.
Posa warns Carlos that it's best if he gives him all of his important documents and letters for safekeeping. For a moment, Carlos wavers about entrusting his most valuable possessions to the king's confidant, but then reassured of their friendship, hands over his papers.
A square before the cathedral in the city of Valladolid. Bells toll as the people merrily await the execution and praise the power of Philip II. The execution procession reaches the square; monks accompany those whom the inquisition has sentenced to death. In their song they praise the power of God. The representatives of the state march out from the palace: Elisabeth and her ladies-in-waiting and pages, Posa and other grandees. They proceed to the steps of the church, whose gates open to reveal Philip wearing his crown. The king swears before God and the people to fight for the Lord with fire and sword. To the astonishment of those present, a group of Flemish emissaries led by Carlos appear before the king and ask him to liberate the Flemish people, with Carlos asking his father to be entrusted with the provinces of Brabant and Flanders. Philip accuses the Flemish of being unfaithful to God and tells Carlos he is mad. The infante draws a sword. Philip orders the assembled lords to disarm Carlos, but nobody dares to seize his sword from him. At last Posa steps forward to carry out the king's order. Despondently, the infante hands over the weapon to the marquis, who bows before the king. The king departs with his wife and court. A celestial voice sounds, calling the poor souls in search of forgiveness and peace to the throne of God.
Flames blaze up around the pyre.
The king's chamber. Philip is bent over a table covered with papers. Dawn. "If the king sleeps, they will betray him; they'll rob him of his crown and his wife." Philip is awake, brooding over the fact that his wife has never loved him. His contemplation is interrupted by the announcement of the arrival of the grand inquisitor.
He has summoned the 90-year-old, blind grand inquisitor in order to ascertain whether the church will absolve him if he removes the rebelling Carlos. "The peace of the world is worth the blood of a son, and God sacrifice his own son for us..." The grand inquisitor wishes to discuss a more important matter: he requests that the reformer Posa be handed over to the church. Philip does not agree to this. The inquisitor coldly informs him that the king himself could be called before the inquisition the next day.
After the priest departs, Elisabeth comes to the king with her grievance: her treasure chest, whose contents were of great value, has been stolen! Philip takes the casket from his table and offers it to Elisabeth, asking her to open it. The stunned Elisabeth refuses, and so the king pries it open himself. Inside Philip finds the portrait of Carlos and admonishes the queen to tremble in fear if she has been unfaithful to him. Overcome with emotion, Elisabeth faints, prompting Philip to call for help. Eboli rushes in, followed by Posa. The king departs with the marquis, and Elisabeth comes to. Eboli is consumed by guilt and admits everything to the queen: not only was she was the one who stole the casket in order to get revenge on Carlos, she is also the king's mistress. Horrified, Elisabeth gives her lady-in-waiting an ultimatum: she must either enter a convent or flee. Eboli curses her own beauty, which has caused her ruin, and decides that she will attempt to save the imprisoned Carlos from execution
Carlos's cell underground. Posa visits the imprisoned infante. The marquis reveals to his friend that by using Carlos's secret documents, he had deflected the suspicions regarding the Flemish uprising towards himself, and thus Carlos would be able to escape. He asks the infante to continue to fight for Flanders in his place. A gunshot rings out: the inquisition has caught up with the marquis. With his last bit of strength, Posa reveals that the queen will be waiting for Carlos in the monastery the next day. Philip arrives with his retinue, intending to free his son. Carlos attacks his father, blaming him for Posa's death. The king now learns of Posa's murder, and grief-stricken, he too mourns Posa.
Elisabeth arrives, followed by Eboli. The princess has crossed the city inciting the people, who from behind the gates are now demanding that the king set Carlos free. Philip has the gate opened. The angry crowd calms down at the sight of the grand inquisitor, falling to their knees before the priest and, at his command, paying homage to the king.
The Monastery of Saint-Just. A moonlit night. Elisabeth kneels before the grave of Charles V. She is waiting for Carlos, whom she had promised Posa to help escape to Flanders. The infante enters, and the two bid each other farewell.
Philip arrives at the church together with the grand inquisitor. They have come for Carlos.... Retreating from the guards the infante backs up toward the grave of Charles V. "My son, peace is found only with God", says the monk who appears behind Carlos. Everybody recognises the monk as Charles V, who proceeds to take the infante with him into the depths of the monastery.