Act I
In Constantinople, the widowed empress Arianna is crowning her new husband, Anastasio, as her consort. The ladies and knights of the court hail the dawning of a new Golden Age. But the celebrations are interrupted by the arrival of Amanzio, the General of the Imperial Army, with news that they are in danger from the rebel Vitaliano. Anastasio instinctively rises from his throne to enter the field against the rebels, but Arianna holds him back.

Polidarte, a messenger from Vitaliano, arrives with the rebel’s demands: Arianna must be surrendered to him and become his wife. Anastasio sends Polidarte back with an angry refusal, and sets off for battle. Left alone, Arianna resolves to follow him to the conflict.

In the fields, Giustino plows the land but aspires to become a soldier. He falls asleep, and in a dream Fortune appears to him and tells him to realise his ambition, for a throne and palace await him. As Fortune and her Wheel disappear, Giustino awakes and prepares for battle.

Suddenly a woman rushes in pursued by a bear. Giustino kills the bear and saves her. She introduces herself as Leocasta, Anastasio’s sister and, observing Giustino’s noble nature and feeling the first stirrings of love, she invites him to accompany her to the palace. Arianna follows her husband into battle and is captured by the rebels. At the palace Giustino is immediately welcomed as Anastasio’s champion, and sent to prove himself by rescuing Arianna.

In the rebel camp Polidarte brings Arianna to Vitaliano. When she rejects his amorous advances he furiously sends her to be thrown to a sea monster that has been terrorising the countryside. Arianna bemoans her fate and declares her faithfulness to her husband.

Act II
The ship carrying Anastasio and Giustuino is wrecked in a storm but they struggle to the shore. They seek shelter in a nearby cottage.

Poldarte enters with Arianna. He gives her one last chance to relent, but she refuses and he leaves her chained to a rock. The sea monster rises from the waters and approaches her. Giustino hears her cries and rushes out to do battle with the monster. He is victorious and releases Arianna. Anastasio joins them and is delighted to be reunited with his wife. He thanks Giustino for his courage. Amanzio arrives and they all leave the shore, accompanied by the voices of the sailors

Regretting his rash action, Vitaliano arrives to save Arianna but discovers the dead sea monster. Not knowing whether she is alive or dead he sets out to find her.

In the palace garden Leocasta sings of her love for Giustino. The victorious Anastasio enters with Amanzio, followed by Giustino dragging Vitaliano, who he has captured, in chains. Anastasio once again thanks Giustino for his courage. Amanzio grows jealous of the simple ploughman who has won such a victory. Giustino suggests that Arianna should decide Vitaliano’s fate, and the rebel is dragged away. Giustino is sent back into the field by Anastasio to complete the defeat of the rebels, and he celebrates his growing reputation.
Vitaliano is brought before Arianna, and begs for one look of love before he dies. She contemptuously refuses and has him imprisoned until the time set for this execution.

Act III
Vitaliano escapes from his prison with the help of his friends. He thanks them and sets off to plot his revenge.

Amanzio starts to sow seeds of suspicion in Anastasio’s mind regarding Giustino. He gives Anastasio a sash encrusted with jewels that he has taken from Vitaliano. Concerned that Giustino might make an attempt on his throne and his wife, Anastasio sends Amanzio to keep watch on Giustino.

Overheard by Amanzio, Arianna praises Giustino’s courage and gives him the jewelled sash that her husband has given to her. Amanzio leaves secretly to tell Anastasio, who is angry at what he hears. He confronts Giustino and Arianna, but will not hear their explanation. He sends Giustino off to be executed, and banishes Arianna.

Leocasta suspects that Amanzio is a traitor, and worries that her growing love for Giustino will be in vain. Amanzio delights in the successful outcome of his plans.

Thanks to Leocasta’s intervention Giustino has been saved from execution, but is now an exile. He scorns Fortune who had promised him a throne and kingdom, and falls exhausted to the ground. Vitaliano enters and, finding the sleeping Giustino asleep raises his sword to kill him in revenge for his previous captivity. But suddenly the mountainside splits open and the voice of Vitaliano’s dead father warns him that he is about to murder his own brother. Vitaliano looks for the distinctive mark of his family – a star on the left arm – and finding it wakes Giustino and reveals their kinship. Vitaliano agrees to join Giustino in his desire to reveal Amanzio’s treachery and restore Arianna to Anastasio.

In a Pleasure Garden, with a great Temple of Fortune, Amanzio mounts the throne with a laurel crown on his head. He celebrates his victory as Anastasio, Arianna and Leocasta are led in in chains. Giustino, Vitaliano and Polidarte rush in with their troops and Amanzio tries to flee. But Giustino captures him and sends him off to be executed. He releases the others from their chains and goes to kneel to Anastasio, who raises him up and embraces him. Anastasio is reunited with Arianna, and begs forgiveness for his error.

Giustino pleads on behalf of his brother, Vitaliano, who is forgiven. Anastasio makes Giustino his co-regent, and offers his sister Leocasta in marriage to him.

All celebrate the happy outcome of events, and join in a final chorus welcoming a new Age of Gold.

(c) Handel House Museum