The noble Don Juan Mendoza has fallen madly in love with Doña Leonor Enríquez, but he cannot marry her because she is the youngest of Don Pedro's two daughters, so he requests the help of his good friend Don Alonso de Luna. The older sister, Beatriz, committs to guard Doña Leonor. Don Alonso will intervene in favor of his friend, trying to make Doña Beatriz fall in love with him, but he will end up facing the pains of love. Assisted by the servants Inés and Moscatel, ladies and gentlemen engage in a series of entanglements from which they will all learn that Love cannot be mocked.