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.

The fourth act is played in front of the Lateran church.  The battle has taken place.  The barons have been repulsed at the cost of great slaughter.  But notwithstanding their losses and the death of their leader, the elder Colonna, the nobles have not relinquished all hope of success.  What they failed to secure by the force of arms, they now hope to win by intrigue, for they have artfully won not only the Pope, but the Emperor also, to uphold their cause and side with them.  The people, who have just learned that the Pope and Emperor have recalled their legates and ambassadors, are awed and frightened.  Baroncelli and Cecco, two demagogues, seize this occasion to poison their fickle minds, and blame Rienzi openly for all that has occurred.  Their specious reasoning that the Tribune must be very wicked indeed, since the spiritual and temporal authorities alike disapprove of him, is strengthened by the sudden appearance of Adrian, who, wild with grief at his father’s death, publicly declares he has vowed to slay the Tribune.  The people—­who, lacking the strength to uphold their convictions, now hate their leader as vehemently as they once loved and admired him—­are about to join Adrian in his passionate cry of ‘Down with Rienzi!’ when the cardinal and his train suddenly appear, and march into the church, where a grand ‘Te Deum’ is to be sung to celebrate the victory over the barons.

While the Romans are wavering, and wondering whether they have not made a mistake, and whether the Pope really disapproves of their chief magistrate, Rienzi marches toward the church, accompanied by Irene and his body guard.  Adrian, at the sight of his pale beloved, has no longer the courage to execute his purpose and slay her only brother.  Just as they are about to enter the church, where they expect to hear the joyful strains of thanksgiving, the cardinal appears at the church door, barring their entrance, and solemnly pronounces the Church’s anathema upon the horror-struck Rienzi.

The people all start back and withdraw from him as from one accursed, while Adrian, seizing Irene’s hand, seeks to lead her away from her brother.  But the brave girl resists her lover’s offers and entreaties, and, clinging closely to the unhappy Tribune, she declares she will never forsake him, while he vows he will never relinquish his hope that Rome may eventually recover her wonted freedom, and again shake off the tyrant’s yoke.