Pastor fido is set in the fictional pastoral land of Arcadia, the idyllic home of shepherds and nymphs that was far removed from the clamorous life of Renaissance cities. In Guarini's play, however, Arcadia is threatened by a curse of the goddess Diana, which requires either the marriage of two descendants of divine lineage or the sacrifice of a chaste nymph in order to spare the people from immeasurable misfortune. Thus it is arranged that Silvio, a young hunter (and a descendant of Achilles) who could care less about love, will marry the fair Amarilli (a descendant of Pan). The play recounts the tangled events of their wedding day.

     All would be well and good for Silvio and Amarilli's wedding, except that Mirtillo (the faithful shepherd) has fallen deeply in love with Amarilli and is determined to win her heart. Yet this is only one of various love triangles that are interwoven throughout the play. Silvio is pursued by the simple Dorinda, whom he later mistakes for a wolf and shoots with an arrow. Mirtillo is pursued by the cunning and deceitful Corisca, whose trap to win over the shepherd nearly gets both Mirtillo and Amarilli killed. Amarilli, in turn, has fallen in love with Mirtillo but must conceal this love and treat him bitterly so that she may marry Silvio and save Arcadia (and maintain societal order). Of course, all expectations and plans quickly fall to shambles in a way that is both tragic and comic...