The Greek Princess Glauce has grave misgivings about her upcoming marriage to Jason, lately arrived in Greece from Colchis with Medea and their children. As Glauce’s maidservants try to reassure her, King Creon promises Jason that his children will be protected, despite the sins of their mother. Medea enters and castigates Jason for his faithlessness. Creon threatens her with imprisonment if she does not leave immediately. Medea, in turn, threatens to kill Glauce if the wedding takes place. Alone with Jason, Medea reminds him of the love they shared and of the deeds she performed on his behalf, including the sacrifice of her brother. Bereft of homeland and family, she begs him to return to her, but he refuses.
Medea learns that her children are to remain in Greece while she is cast into exile. Meanwhile, the people call for Medea’s blood. Creon urges Medea to leave as quickly as possible, but Medea successfully petitions him for one more day in Greece. Medea begs Jason to restore her children to her. He consents to allow her their company until her departure. Medea gives Neris, her maidservant, an enchanted robe and crown to present to Glauce at the wedding.
Neris brings Medea’s children to her. Overcome with maternal love, she falters, but then resolves to kill the children to punish Jason. Neris confirms that she has delivered Medea’s wedding gifts to Glauce; Medea reveals that the princess will be fatally poisoned by the crown. Neris begs Medea to let this act suffice as revenge, but Medea cannot bear to leave her children with the man who has treated her so cruelly. Jason, having just witnessed Glauce’s death, arrives to confront Medea in the surprising final scene of this gripping tragedy.