The attendants now announced that the King and a company of soldiers were clamouring at the gates for admission; and when Ernani had been hastily concealed in a secret chamber, and Elvira had retired to her own apartment, Don Carlos was admitted. The young King announced that he had scattered the bandit hordes, and now sought their chief; and adding that he had tracked Ernani to Castle Silva, he sternly demanded that he should be delivered up to him.
This command Don Silva stubbornly refused to carry out; whereupon the King gave orders for the castle to be searched. The soldiers, however, being unacquainted with the secret chamber, were unable to find the bandit; and then Carlos, furious at being defied, declared that if Ernani's head were not forthcoming he would take Don Silva's.
Whilst the nobleman was still protesting against betraying one who had been his guest, hoping thus to reserve Ernani for a more cruel fate, Elvira hastily entered the hall, and, falling on her knees before the King, she besought him not to engage in strife, but to have mercy on his foes.
On beholding the beautiful Elvira again the King's suppressed love for her burned fiercely once more; and, taking her gently by the hand, he declared that he would now hold her as a hostage for the good faith of Don Silva, until Ernani should be delivered up to him. It was in vain that Don Silva protested against such a proceeding; and the weeping Elvira was at once taken away by the King to his palace.
When Ernani was at length led forth from his hiding-place, and learned that his beloved one was held as a hostage by the King, he was furious; and now regarding Don Silva as a companion in misfortune, he offered to join him in a scheme of vengeance against Carlos, who was their mutual enemy and rival in the affections of Elvira. Regarding his life, however, as forfeited to Silva, to whom he was grateful for having protected him so long, Ernani declared his willingness to die whenever his rival should desire it; and as a pledge of his solemn promise, he gave the nobleman his hunting-horn, saying, "By this token, in the hour when thou wilt have Ernani perish, sound this horn, and I shall know it is the hour for me to die!"
Don Silva, thus recognising that he had Ernani in his power, gladly accepted him as a colleague in taking vengeance on the King; and the pair immediately sought out a band of conspirators who were at that time seeking to assassinate Carlos, who had not yet been unanimously accepted as King, and offered to join them in their enterprise. They were eagerly welcomed by the conspirators; and it was arranged that they should meet on a certain day in the Catacombs of Aquisgrano, and, by drawing lots, decide who should strike the fatal blow.
Meanwhile, Carlos had received information that a conspiracy had been formed against him; and as he was now almost certain of being accepted as King by the majority of the people, he bravely determined to face his secret foes and denounce them. He therefore bade his esquire to cause three salutes of cannon to be sounded should he be accepted as King at the final meeting of Electors to be held that day, that he might be sure of his regal power before denouncing his foes; and he also gave orders for the Ministers of State, together with the Lady Elvira, to be brought to him in the conspirators' meeting-place.
He then made his way alone to the Catacombs of Aquisgrano, and took up a position beside the mausoleum of his illustrious father, Charles the Great; and here many solemn and noble thoughts passed through the mind of the young prince. The sacred responsibility of his high position impressed itself upon him for the first time, so that a sense of his own frailty and weakness made him humbly conscious of his utter dependence upon a Higher Power than his own; and he solemnly registered a vow that if his kingship should be accepted that day, he would forego the careless pleasures and passions of youth, and devote himself loyally to the service of his country and people, and thereby win for himself a glorious name and virtue's "crown of deathless fame."
Having made this sacred resolve, the young King now concealed himself in the royal mausoleum, from whence he could see and hear all that passed without being observed; and a few minutes later the conspirators entered, all wrapped in long dark cloaks. Don Silva and Ernani had established themselves as the leaders; and after reciting their hatred of the monarchy, they drew lots for the privilege of killing the young Carlos.
The name drawn was that of Ernani; and Don Silva, greatly disappointed, entreated the bandit to resign the right in his favour. Ernani, however, refused to forego his privilege; and in spite of Silva's angry warning that his vengeance should quickly follow, he firmly declared that he alone should kill his royal rival.