Four Spanish aristocrats, members of the same family, are walking in a meadow. Lisauro and Ismenia are brother and sister, the children of Bellides; they are accompanied by their relations, Terzo and Aminta. They encounter Antonio and his friend Martino. Antonio is the nephew of Julio, and Julio and Bellides are enemies — which affects all the members of their respective families. The men in the two parties draw their swords and prepare to fight, but Ismenia and Aminta prevail on them to part peacefully. Ismenia has a special motive in this: she has fallen in love with Antonio at first sight. She sends Aminta to him with a love letter, inviting him to court her at her window that evening. Antonio is attracted to Ismenia, and taken with her invitation. His friend Martino is at first cynical about romance; but Antonio's growing passion is contagious, and Martino decides to pursue Ismenia himself.