Not so the Princess Eboli, wife of Ruy Gomez, the tutor of Carlos. Having tried to win the love of the king and found her designs thwarted by the queen's beauty, Eboli makes advances to Prince Carlos, who lets her know that he cannot love her and thus makes her angry. In this mood she bestows her favor upon the king's half-brother, Don Juan of Austria, who is also enamored of the queen and has been watching Carlos suspiciously. Having thus made enemies of Eboli and Don Juan, Carlos next draws upon himself the hatred of the powerful Duke of Alva, of Ruy Gomez, and of the Inquisition. This he does by his outspoken criticism of their doings and his threats of punishment to be meted out to them when he shall have become king. Anxious for their own future Alva and Ruy Gomez conspire together and cause suspicions of Carlos to be whispered in the ear of the king. At first Philip is not greatly excited. When Carlos, importuned by Count Egmont, asks for a commission to the Netherlands, Philip does not refuse, but declares that he will go too and share the peril of his son. This, however, is a mere ruse to gain time. While they are waiting, the king meanwhile feigning illness, Carlos communicates freely with the queen through his bosom friend, the Marquis of Posa. Hearing of this intimacy the king now becomes really jealous, but of Posa not of Carlos. Maddened by suspicion he has the marquis murdered on the street and employs Eboli to watch the queen. After this Carlos resolves upon independent action and begins to negotiate with the Netherlanders. His operations are watched and reported by his enemies, and just as he is about to leave Spain he is arrested. The king places his case before the Holy Office, which decrees that he must die. Being allowed to choose the manner of his death he opens his veins while bathing.
With the actual Don Carlos, whose story bears but little resemblance to that of St. Réal's hero, we are not particularly concerned. The French Abbé's drift is to exalt the French princess and to give a telling picture of a pair of high-minded lovers who are brought to their death by a complicate intrigue begotten of jealousy, political hatred and religious fanaticism. After the death of Carlos the queen is poisoned and then, one after the other, all the conspirators meet with poetic justice. "Ainsi", the Abbé concludes, "furent expiées les morts à jamais déplorables d'un prince magnanime, et de la plus belle et de la plus vertueuse princesse qui fut jamais. C'est ainsi que leurs ombres infortunées furent enfin pleinement appaisées par les funestes destinées de tous les complices de leur trépas."