Act I

Aristea, daughter of the king of Sicione, Clistene, has been promised to the victor in the coming Olympic games; however, she loves, and is loved by Megacle. Licida, whom all believe to be the son of the king of Crete, aspires to Aristea's hand. Licida knows that he cannot win the Olympic games and therefore asks his friend Megacle, whose life he had once saved, to participate for him in the competition. Megacle agrees and, having left Crete, arrives just in time to take part in the games under the name of Licida. Only after he has gone through the formalities does Megacle discover, from his friend Licida, that the victor will win the hand of Aristea. Despite the pain and anguish that this discovery brings him, Megacle decides to respect the pact of honour that binds him to his friend and to compete in Licida's stead, thus renouncing for ever the love of Aristea.

Meanwhile Argene, a Cretan lady who is concealing her true identity under that of a shepherdess Licori, to whom Licida had once sworn love, has learnt that Megacle is to fight under a false name on behalf of Licida and has thus realised that Licida no longer loves her. Aristea and Megacle meet, but Megacle has not got the courage to tell his beloved that he Is competing in the games not for himself but for his friend Licida.

Act II

Megacle has won the Olympic competition, casting Aristea into dejection, for she has seen him triumph under the name of Licida. After a dramatic conversation in which he affempts to convince Aristea to accept Licida as her husband, Megacle leaves his beloved intent on taking his own life. In desperation Aristea rejects Licida, whilst Argene informs the king of the exchange of identities.

Act III

Licida in his rage at having been exiled for trickery attempts to kill the king, but is arrested and condemned to death. Megacle, whose attempted suicide has failed, tries to save him but in vain. Aristea also tries, with no success, to convince her father. When the sentence is about to be carried out, Argene, as Licida's promised bride, asks the king to allow her to take Licida's place and undergo his sentence. Licida denies that she is his promised bride, but the girl proves her affirmation by showing them a necklace that Licida himself had given her. The king recognises this as the jewel that had hung round the neck of one of his children whom he had had cast out to the mercy of the sea, since a prophecy had foretold that this son would have made an attempt on his father's life. The king and his confidant Alcandro thus recognise Licida as the king's son and twin brother of Aristea. Licida is pardoned, and the announcement of the weddings of Megacle and Aristea, Licida and Argene concludes the opera amidst general reloicing.