The story is based upon a genuine medieval manuscript discovered in a library in Blois. Writer Alfred Blau was the one to stumble upon it, and thinking its magical and romantic elements would make for good theater, he collaborated on a libretto with poet Louis de Gramont. They began their tale in Byzantium, where sorcerer-emperor Phorcas is about to turn over his throne and his magic to his daughter, Esclarmonde, provded she remain veiled until she is twenty. She has fallen in love with the French knight Roland, whom she has met only once, and she uses her new powers to call upon spirits to bring her beloved to an island. In Act II, it is at this island where she promises him riches and her love on the condition he never lift her veil; he accepts. She then sends him on a mission to rescue Blois from the invading Saracens, telling him that he will remain safe so long as he keeps his oath to her. She also promises to magically travel to visit him nightly while he is away. (This would sugest that this will make keeping that veil down a tetch difficult, but remember that chivalric code what it was, she was to remain pure during those visitations.)
Act III finds us in Blois, where the dare I say beknighted Christians of the besieged city have been ordered to hand over a hundred virgins to the Saracens' leader. Roland arrives and defeats the invaders. When the king of Blois offers Roland the hand of his daughter as thanks (women being thought of as property in one days, the irony of the situation never occurred to him), the Frenchman -- faithful to Esclarmonde -- turns down the offer. But it's literally damned-if-you-do, damned-if you-don't: The local bishop threatens Roland with eternal damnation unless he explains his reasons for his refusal, and then when he learns Roland loves a pagan enchantress, he withholds absolution from him anyway. While Esclarmonde is visiting her beloved that night, the bishop and his followers storm the room and tear the veil from her in an exorcism rite. Roland's heretofore invincible sword shatters because of his vow to her has been nullified (even though it was not he who removed the veil), and the enchantress vanishes.