Although the play, which had premiered two years earlier, was considered one of D'Annunzio's greatest works, the opera did not achieve a comparable success and has been rarely performed since its day.

The father Lazaro di Roio is happy because his young son Aligi is getting married with a rich woman of the country.

The girl named Mila is accused by the superstitions of the people of being a witch, and so is likely to be sentenced to death.

Aligi and Mila go to live in exile in the Cave, hated by all the people, and plan to leave the country.

When he returns confident, Aligi discovers that the inhabitants of Lama Peligni burned alive Mila during his absence.