Act I. The shepherd Alain and the shepherdess Grisélidis, herding their flocks and piping their lays together, are vastly in love with each other. But the powerful and wealthy Marquis de Saluzzo comes between them, and Grisélidis listens to his voice, and jilts her Alain. In due time a son is born to her, who is christened Loys. Just at this time the marquis feels an overpowering desire to fight the infidels. The priest tries hard to dissuade him from this adventure, buthe will not heed. In his arguments with the marquis the priest has much to say about the devil and his cunning schemes for leading men and particularly women astray. Long absence of her lord would not be good for Grisélidis. However, the marquis goes forth to fight the Saracens and leaves his charming wife to all the temptations the devil can devise. So sure of his wife is the marquis that he even hands the devil his wedding ring, a very foolish thing for a departing husband to do.
Act II. The scene changes to a pretty garden overlooking the sea. The devil and his wife (Fiamina) argue with Grisélidis that the latter should become housekeeper during the absence of the marquis. After settling this point Fiamina facilitates the appearance at the castle of Alain, one-time wooer of Grisélidis, who makes good use of his opportunity. But in the nick of time Loys, the baby son of Grisélidis, saves his mother from infidelity and perdition. At this the devils is so wroth that he seizes the little fellow and runs off with him to parts unknown.
Act III. However, his satanic majesty keeps on tempting the pretty grass widow. His next move is an offer from him to return the child to the mother if she will but give him a kiss, one measly little kiss. Grisélidis is in doubt; she hesitates. But again chance favors her, for her truant husband, the marquis, returns from fighting the Saracens precisely at the time when the devil has left to the young wife only the above alternative. The marquis is mightily aggrieved at the disappearance of his son and heir and makes up his mind to search for him high and low. The devil, however, causes the weapons to vanish without which in those days searching parties could not get along. Thereupon he and his wife, scenting something fiendish, begin to pray earnestly. Then the triptych over the altar opens and lo! the boy walks out of it.