Synopsis

ACT I

The curtain rises on a municipal celebration.  Argirio and Orbazzano, the heads of two warring noble families, have declared civil peace in the face of a dangerous external threat. As a conciliatory offering, Argirio has promised his daughter, Amenaide, to Orbazzano in marriage. The men summon Amenaide and pronounce her fate, insensitive to the fact that she loves Tancredi, who has not only been exiled on pain of death, but whose lands and titles have also been unfairly distributed to Orbazzano.  Meanwhile, from Amenaide's close friend Isaura, we learn that Amenaide has sent a messenger with a love letter intended for Tancredi, whom she has heard is near the city walls. In an effort to protect her beloved's identity, however, she did not directly address the letter.  Amenaide dutifully consents to her father's decision and leaves, accompanied by Isaura.

Tancredi and his page Roggiero arrive in disguise. After Tancredi sings of the love he still feels for the country that wronged him, he sends Roggiero to scout the territory while he conceals himself in a garden near Amenaide's home. Amenaide appears with Argirio. He informs her that Solamir now wishes to marry her in order to force an alliance, and that she must therefore marry Orbazzano immediately.  Argirio leaves and Tancredi approaches Amenaide. She pleads with him to flee and save his life, even though she is overjoyed to see him. Once she leaves, the heartbroken Tancredi overhears news of her impending wedding and swears vengeance on Orbazzano and curses Amenaide.  The city assembles for the wedding, where Tancredi presents himself to Argirio as an unknown soldier who wishes to join the fight against the enemy.  Argirio does not recognize Tancredi and accepts the offer, just as Orbazzano bursts in with Amenaide's unaddressed letter to Tancredi, announcing that, because it was intercepted at enemy gates, it must have been intended for Solamir. Furious, Argirio disowns his daughter and Tancredi renounces his former love. Orbazzano sentences Amenaide to death.

ACT II

Isaura pleads with Orbazzano to pardon Amenaide, but he informs her that Amenaide has been sentenced to death almost unanimously — only her father's name remains unsigned.  Argirio arrives and almost succumbs to his conscience, but finally signs the document. Isaura lashes out at Orbazzano and prays to God to protect Amenaide in the hour of her death.

Amenaide is praying in prison when her father and Orbazzano arrive.  Argirio confesses that he still loves Amenaide and plans to comfort her in death, and Tancredi bursts through the prison gates and declares his intention to duel Orbazzano and defend the accused.  Obazzano accepts his challenge.  Once the men leave, Isaura arrives to comfort her friend and the two women pray for divine protection.  Soon after, Argirio and soldiers return with news that Tancredi has killed Orbazzano; Amenaide will be set free.

Tancredi receives a grand municipal celebration, but he remains heartbroken and intends to leave as soon as possible. Amenaide intercepts him, only to learn that, despite the fact that he fought for her honor, he still considers her a traitor and cannot love her.  Distraught, she pursues him as he leaves.  Left alone with Roggiero, Isaura confides in him:  She alone knows that Amenaide has been faithful to Tancredi, and that she alone can reverse the lovers' fate.  As Isaura goes out, a doubtful Roggiero sings of the happiness Tancredi might feel if Amenaide is proven innocent.

The city is under attack, but Tancredi has already travelled far outside its borders.  Argirio, Amenaide, Isaura and the soldiers, having learned his true identity, find him at last.  Tancredi agrees to return with them, determined to die in service to his country.  Argirio soon comes back with cold comfort for Amenaide:  Tancredi has defeated the enemy, but has incurred fatal wounds in doing so. Amenaide rushes to his side and begs for absolution.  Too late, Argirio reveals the truth: The letter was written to Tancredi, and Amenaide is innocent of all charges.  In accordance with Tancredi's final wishes, Argirio marries the lovers and Tancredi dies in his wife's arms.