Paolino has secretly married Geronimo's daughter Carolina. Their situation is complicated by Carolina's aunt Fidalma, who loves Paolino, and by the arrival of the Englishman Count Robinson who, although betrothed to Geronimo's other daughter Elisetta, falls in love with Carolina. After much scheming and amorous intrigue, the truth about the marriage is revealed and all ends happily.

The story takes place in Corinth, in Creon's palace. Glauce (the king's daughter) is making preparations for her wedding with Jason; the hero has repudiated Medea, his wife - with whom he had two children - who once helped him to recover the Golden Fleece. The Argonauts arrive to pay homage to the bride, who cannot hide her fear of Medea. Medea manages to enter the king's palace and begs for Jason's return; when he refuses, the sorceress curses him and swears vengeance; then, alone with him, she recalls the happy moments of their love. Creon orders Medea to leave Corinth and she pretends to agree, obtaining permission to spend one more day with her children; meanwhile, she orders Neris, her maidservant, to take to Glauce her wedding present: the diadem and mantle given to her by Apollo.