The ballet opens with Bertram, Robert le Diable's father, entering the ruined cloister of Sainte-Rosalie. He summons the ghosts of nuns who have violated their vows. They rise from their graves. He orders them to seduce his son Robert into accepting a deadly talisman. The Abbess Helena orders the ghosts to waltz. In spite of their sacred vows, the nuns waltz. The dead nuns give themselves over to unholy thrills.