When they have all gone in obedience to his command, the Tribune, for such is the dignity which the people have conferred upon their champion Rienzi, turns toward the girl, the innocent cause of all the uproar, and perceives for the first time that it is his own sister Irene. Adrian is bending anxiously over her fainting form; but as soon as she recovers her senses she hastens to inform her brother that he saved her from Orsini's shameful attempt, and bespeaks his fervent thanks for her young protector.
It is then only that the Tribune realises that a Colonna, one of his bitterest foes, and one of the most influential among the hated barons, has overheard his instructions to his adherents, and can defeat his most secret and long cherished plans. Suddenly, however, he remembers that in youth he and Adrian often played together, and, counting upon the young nobleman's deep sense of honour, which he had frequently tested in the past, he passionately adjures him to show himself a true Roman and help him to save his unhappy country. Irene fervently joins in this appeal, and such is the influence of her beauty and distress that Adrian, who is very patriotic and who has long wished to see the city resume its former splendour, gladly consents to lend his aid.
This oath of allegiance received, Rienzi, whom matters of state call elsewhere, asks Adrian to remain in his house during his absence, to protect his sister against a renewal of the evening's outrage. Adrian joyfully accepts this charge, and the lovers, for they have been such from the very first glance exchanged, remain alone together and unite in a touching duet of faith and love, whose beautiful, peaceful strains contrast oddly with the preceding discordant strife. In spite of his transport at finding his affections returned, and in the very midst of his rapturous joy at embracing his beloved, Adrian, tortured by premonitory fears, warns Irene that her brother is far too sanguine of success, and that his hopes will surely be deceived. He also declares that he fears lest the proverbially fickle people may waver in their promised allegiance, and lest Rienzi may be the victim of the cruel barons whom he has now openly defied. The lovers' conversation is interrupted at sunrise by the ringing of the Capitol bell, proclaiming that the revolution has begun, and the triumphant chorus of priests and people is heard without, bidding all the Romans rejoice as their freedom is now assured. Riding ahead of the procession, Rienzi slowly passes by in the glittering armour and array of a Tribune, and from time to time pauses to address the crowd, telling them that the ancient city is once more free, and that he, as chief magistrate, will severely punish any and every infringement of the law. At the news of this welcome proclamation the enthusiasm of the people reaches such an exalted pitch that they all loudly swear to obey their Tribune implicitly, and loyally help him to uphold the might and dignity of the Holy City:—
‘We swear to thee that great and free
Our Rome shall be as once of yore;
To protect it from tyranny
We'll shed the last drop of our gore.
Shame and destruction now we vow
To all the enemies of Rome;
A new free people are we now,
And we'll defend our hearth and home.’
The scene of the second act is laid in the Capitol, where the barons, who had been forced to take the oath of allegiance ere they were allowed to re-enter the city, are present, as well as the numerous emissaries from foreign courts. Heralds and messengers from all parts of the land crowd eagerly around the Tribune, anxious to do him homage, and to assure him that, thanks to his decrees, order and peace are now restored.
Amid the general silence the heralds make their reports, declaring that the roads are safe, all brigandage suppressed, commerce and agriculture more flourishing than ever before, a statement which Rienzi and the people receive with every demonstration of great joy. To the barons, however, these are very unwelcome tidings, and, knowing that the people could soon be cowed were they only deprived of their powerful leader, they gather together in one corner of the hall and plot how to put Rienzi to death.
Adrian accidentally discovers this conspiracy, and indignantly remonstrates with the barons, threatening even to denounce them, since they are about to break their word and resort to such dishonourable means. But his own father, Colonna, is one of the instigators of the conspiracy, and he dares him to carry out his threat, which would only result in branding him as a parricide. Then, without waiting to hear his son's decision, the old baron, accompanied by the other conspirators, joins Rienzi on the balcony, whence he has just addressed the assembled people. They have been listening to his last proposal, that the Romans should shake off the galling yoke of the German Empire and make their city a republic once more, and now loud and enthusiastic acclamations rend the air.
The speech ended, Adrian, stealing softly behind the Tribune, bids him be on the watch as treachery is lurking near. He has scarcely ended his warning and slipped away ere the conspirators suddenly surround the Tribune, and there, in the presence of the assembled people, they simultaneously draw their daggers, and strike him repeatedly. This dastardly attempt at murder utterly fails, however, as the Tribune wears a corselet of mail beneath the robes of state, and his guards quickly disarm and secure the conspirators while the people loudly clamour for their execution by the axe, a burly blacksmith, Cecco, acting as their principal spokesman.
Rienzi, who is principally incensed by their attack upon Roman liberties, and by their utter lack of faith, is about to yield to their demand, when Irene and Adrian suddenly fall at his feet, imploring the pardon of the condemned, and entreating him to show mercy rather than justice. Once more Rienzi addresses the people, but it requires all his persuasive eloquence to induce them, at last, to forgive the barons' attempt. Then the culprits are summoned into the Tribune's august presence, where, instead of being executed as they fully expect, they are pardoned and set free, after they have once more solemnly pledged themselves to respect the new government and its chosen representatives. This promise is wrung from them by the force of circumstances; they have no intention of keeping it, and they are no sooner released than they utter dark threats of revenge, which fill the people's hearts with ominous fear, and make them regret the clemency they have just shown.
The next act is played on one of the public squares of Rome, where the people are tumultuously assembled to discuss the secret flight of the barons. They have fled from the city during the night, and, in spite of their recently renewed oaths, are even now preparing to re-enter the city with fire and sword, and to resume their former supremacy. In frantic terror, the people call upon Rienzi to deliver them, declaring that, had he only been firm and executed the nobles, Rome would now have no need to fear their wrath. Adrian, coming upon the spot as they march off toward the Capitol, anxiously deliberates what course he shall pursue, and bitterly reviles fate, which forces him either to bear arms against his own father and kin, or to turn traitor and slay the Tribune, the brother of his fair beloved. While he thus soliloquises in his despair, Rienzi appears on horseback, escorted by the Roman troops, all loudly chanting a battle song, of which the constant refrain is the Tribune's rallying cry, ‘Santo Spirito Cavaliere!’ They are on their way to the city gates, where the assembled forces of the barons await them, and Adrian, in a last frantic attempt to prevent bloodshed, throws himself in front of Rienzi's horse, imploring the Tribune to allow him to try once more to conciliate the rebel nobles. But Rienzi utterly refuses to yield again to his entreaties, and marches calmly on, accompanied by the people chanting the last verse of their solemn war-song.