No sooner had he spoken these fatal words, than Amonasro, having thus learnt the secret he had longed to possess, sprang from his hiding-place, and boldly approaching the lovers, announced to the young Egyptian that he was the King of Ethiopia.
Radames was now overcome with dismay that he had, though unconsciously, betrayed his country's cause into the hands of her enemies; but Amonasro, declaring that no blame could ever attach to him, entreated him to join the Ethiopian ranks, where glory awaited him, and the hand of Aïda should be his reward.
At that moment, however, the Princess Amneris, and Ramphis, the High Priest, emerged from the Temple, having heard all that had passed; and calling to the guards, they bade them seize the three offenders at once. Radames, calling to Amonasro and Aïda to fly for their lives, engaged the attention of the guards until he knew that the Ethiopian King and his daughter had escaped to a safe distance; and then, nobly scorning to avoid the just wrath of the monarch whom he had so unwittingly betrayed, he yielded himself without a struggle into the hands of the High Priest, and was carried away captive to await his doom.
A few days later, Radames was brought to the Hall of Judgment within the royal palace, to be tried as a traitor, and to receive the sentence of death; but as the guards were conducting him thither, they were accosted by the Princess Amneris, who imperiously demanded to speak with the prisoner.
The guards having fallen back respectfully, Amneris addressed Radames, asking him if he was prepared to die the death of a traitor, or if he desired to live; for the proud Princess was still unable to repress the love which consumed her, in spite of her anger that it was not returned, and she was determined to offer the object of her affections a means of saving his life.
Radames, however, answered sorrowfully that he had no further desire to live, since Aïda was lost to him for ever; for he believed her to be dead, and in his grief he even accused the Princess of being the cause of her death. But Amneris declared that this was not so, since Aïda still lived; for though her father had been slain in the battle that had just taken place, his daughter had managed to escape, though none knew of her whereabouts.
Then, with passionate earnestness, Amneris besought Radames to renounce all thought of Aïda for ever, thus hoping that she might herself reign in his heart at last; and she added that if he would do so, she would intercede for his life with the King, who loved her so well that he would grant her even so great a request as this. But Radames declared staunchly that no power on earth could ever induce him to thrust the dear image of Aïda from his heart; and since his beloved one was now lost to him, he should welcome death with gladness.
"Go, then, and die!" cried Amneris, enraged that her love should be thus slighted yet again; and then, as Radames passed into the Hall of Judgment, she burst into a wild paroxysm of weeping, knowing that nothing could now save him, since once in the presence of his judges, his doom was sealed.
Full of remorse that she had not called him back, she crouched near the portal, and listened to what passed within; for though in her heart she realised that Radames was innocent, yet she knew that he would be condemned, since he had done, though unwittingly, a traitor's deed.
To the accusations made against him, Radames answered not a word, for in spite of his clear conscience, he also knew that defence was useless; and when the High Priest pronounced the doom of living incarceration as the traitor's sentence, he bowed his head in resignation, having no longer the desire to live.