Jason
PROLOGUE
Apollo and Cupid debate the outcome of the drama that is about to unfold. Apollo champions Medea as a wife for Jason, while Cupid supports the cause of Hypsipyle.
ACT I
Hercules (Ercole) has persuaded Jason (Giasone) to abandon his betrothed, Hypsipyle (Isifile), and continue his quest for the Golden Fleece. Jason finds himself on Colchis, where he becomes the lover of the queen Medea, without realizing her identity. Medea returns Jason's love and rejects her betrothed Aegeus (Egeo).
Orestes (Oreste), a friend of Hypsipyle, tries unsuccessfully to cross-examine Demo, the stuttering servant of Aegeus.
Medea and Jason meet and, to his delight, she identifies herself as his lover and the mother of his two children.
Employing her supernatural powers, Medea invokes Pluto ("Dell'antro magico") to assist Jason in his quest.
ACT II
Hypsipyle waits for news of Jason. On learning of Jason's love for Medea, she resolves to go to Colchis.
Meanwhile, Jason captures the Golden Fleece, after killing the monsters who guard it.
On the journey home the gods wreck Jason's and Medea's ship and bring them to Hypsipyle's island home in order to ensure Jason's marriage to her. When she appears, Jason denies all knowledge of her and claims she is mad.
ACT III
Jason is persuaded to kill Hypsipyle by the jealous Medea, and orders Besso, one of his guards, to carry out the murder. But the plan goes wrong and Besso throws Medea into the sea instead of Hypsipyle.
She is saved by Aegeus and is forced to acknowledge his fidelity as he swears revenge on Jason. As Jason sleeps, Aegeus attempts to kill him, but is stopped by Hypsipyle.
Seeing Hypsipyle alive, Jason is told by Besso of the death of Medea. Medea appears, accompanied by Aegeus, and encourages Jason to return to Hypsipyle, but he refuses. However, Hypsipyle's lament ("Infelice, che ascolto") wins him back and the opera ends in joyful reconciliation.