Various rustics sing the praises of Louis XIV and call down Glory, Victory and the goddess of war.
Victory tells how she resides in France because of the country's wise ruler who desires to bring peace to the world.
The sorceress Medea (Médée) and her husband Jason are in Corinth, under siege from the Thessaliens for plotting against their king. Creon (Créon), king of Corinth, has allied himself with Orontes (Oronte), prince of Argos, by promising him that he can marry Creon's daughter Creusa (Créuse). Medea rightly suspects Jason of loving Creusa.
Medea is asked to leave Corinth by Creon, since his people fear her presence. Creon proceeds to encourage the love between Jason and his daughter.
Medea warns Orontes about Jason and Creusa, who, it emerges,are to marry with Creon's blessing. Medea infuses with poison the robe she has promised to give to Creusa.
Creusa enters wearing the robe but the poison has not yet taken effect. Medea tells Crontes that the marriage between Jason and Creusa will not take place. She warns Creon that unless his daughter marries Orontes, she will never leave Corinth. Creon attempts to arrest her, but Medea turns his guards against each other and invokes her magic powers to drive the king mad.
Creusa begs Medea to restore her father's sanity. Medea agrees, but the news arrives that Creon has killed Orontes and then himself. Creusa seeks vengeance, but Medea makes the poison in her robe begin to work. Upon finding the princess dying, Jason swears revenge, but is mocked by Medea who tells him that she has killed their children. The opera ends with Medea's destruction of the palace.