Libretto by Pietro Metastasio, first set by Antonio Caldara (1736, Vienna).
Fearful of his power and fame, the people of Athens have driven Themistocles from the city. He believes that his daughter, Aspasia, dispatched to Argos for safety, has perished in a shipwreck, and with his son, Neocle [Neocles], has taken refuge in the land of his enemy, Serse [Xerxes], King of Persia, where he remains unrecognized. Meanwhile, Aspasia, rescued from the sea, has become attendant to the Princess Rossana [Roxana], now residing in Susa.
Aspasia learns from Sebaste [Sebastes], confidant of Xerxes, that there is a price on her father’s head, information that she conveys to him when the two meet and recognize each other. She is in love with Lisimaco [Lysimachus], the Athenian ambassador, who arrives in Susa in search of Themistocles. A friend of Themistocles, but bound by patriotic duty, Lysimachus entreats Xerxes to return the fugitive to Athens to stand trial, but Xerxes refuses and Lysimachus departs. Unexpectedly, Themistocles reveals himself to the king who, admiring his courage, befriends him and offers him refuge. Roxana, in love with Xerxes, suspects Aspasia of being a rival and joins with Sebastes, now resentful of the king’s new friendship, in a conspiracy against the throne....