The Middle Ages
It is spring. The engagement of Anna to Roberto is being celebrated in a village in the Black Forest. Roberto is about to leave for Mainz to claim the inheritance left to him by his deceased aunt. Anna lets her loved-one leave reluctantly; she is being tortured by dark premonitions, and Roberto's repeated promises to remain faithful fail to dismiss her fears. Finally, Roberto asks Anna's father for his blessing and sets off.
Roberto forgets all about Anna almost as soon as he arrives in Mainz. He succumbs to the charms of a beautiful courtesan, lives off the fat of the land and decides not to return to the village. Anna's hopes of being reunited with her loved-one dwindle from day to day. Ultimately, unable to bear her grief any longer, she dies of heartbreak.
The following winter. Guglielmo cannot get over the death of his child and summons the Villi. These are the spirits of virgins who have died of a broken heart and who live in the dark forest. He asks the spirits to take Anna's soul and to avenge her death, but he soon regrets his unchristian request, begging God for forgiveness. Roberto has decided to return to the village in the meantime and meets up with Anna's ghost at the edge of the forest. He thinks she is still alive and wants to embrace her. Anna tells him just how much his absence hurt her, how she suffered and finally died. Roberto is broken-hearted and deeply regrets his unfaithfulness. He suddenly finds himself surrounded by Villi and other spirits, who hound him to death with their frenzied round dance.