The genesis of Thaïs is linked to one of the most famous sopranos of that time, Sybil Sanderson, for whom Massenet had already composed Esclarmonde. Later on, she took part in many reruns of Manon at Opéra -Comique of Paris. A beautiful woman, who was also Massenet's lover, Sanderson had the ideal body to play the protagonist, as well as the amazing vocal skills to reach high-pitched notes. Once the opera was completed, it debuted on the 16th of March 1894, but after a rather cold welcome, the composer revised the musical sheet making some changes, in order to put it back on stage, four years after. In both versions, we find the méditation, with the violin and harp, a page which has then become really popular. Through the lyricism, the spiritual suspension describes the miracle of the protagonist's conversion, which is carried out through the whole opera and becomes, in fact, the reason behind the repentance and salvation of Thaïs.
Egypt, fourth century A.D. The monk Athanaël is greeted by Palémon and other monks. He tells them how he found the city of Alexandria in a state of sin and under the influence of the courtesan Thaïs. Athanaël believes her behaviour is an affront to God and he is wants to convert her to a life of faith. At night he has a vision of the courtesan and he's even more determined to save Thaïs’ soul. Palémon warns him not to interfere. Athanaël arrives to the house of the wealthy friend, Nicias, who tells him that Thaïs is his mistress of the moment, but that he will soon lose her since he has run out of money. Athanaël replies that he has come to convert her. Nicias laughs and warns him that Venus will take revenge for it, but he agrees to introduce him to her. Thaïs appears, Athanaël confronts her and tells her his intention and she asks why he denies his true nature and for love. She starts taking off her clothes but the monk leaves saying he will wait for her at her house.
Thaïs, alone in her bedroom, meditates on the superficiality of her life, she wonders what will happen once her beauty fades. Athanaël arrive, she warns him not to love her, to which he explains the love he's going to teach her, a love that it will lead to eternal life and salvation. Once she hears the voice of Nicias, she rejects both her life of luxury and Athanaël’s God, collpasing in despair. Athanaël says he will wait for her outside. After a night of deep meditation, Thaïs tells Athanaël she is ready to follow him to the convent of Mother Albine. She agrees on burn her palace and all her belongings as he says but asks to keep a statue of Eros, which Athanaël smashes. Nicias arrives declaring he wants to keep Thaïs as his mistress since he's won some money. A dancer performs a ballet, accompanied by the singing of Nicias’s slave girls, and Thaïs and Athanaël reappear from the palace. When the monk announces her conversion, the crowd threatens to stone him for taking Thaïs away. Nicias distracts them by throwing money around and Athanaël and Thäis flee while her palace goes up in flames.
Thaïs is exhausted from the journey through the desert so they rest at an oasis and the monk tells her to be strong. However, her feet are bloody so he feels pity and he goes get water. Thaïs thanks him for bringing her to salvation. At the convent, Albine and the nuns welcome Thaïs and Athanaël realizes that he will never see her again. At the monks’ retreat, Athanaël confesses that he can't stop thinking about Thaïs’s beauty. In fact, while asleep, Athanaël dreams of Thais as a temptress and then as a saint about to die. Waking, he decides to go back to her. Athanaël arrives at the convent and sees Thaïs who's dying. The monk tells her she has converted him to love but Thaïs dies with a vision of angels greeting her in heaven. Athanaël begs God for mercy.