Paphnuce, an ascetic hermit of the Egyptian desert, journeys to Alexandria to find Thais, the libertine beauty whom he knew as a youth. Masquerading as a dandy, he is able to speak with her about eternity; surprisingly he succeeds in converting her to Christianity. Yet on their return to the desert he becomes fascinated with her former life. She enters a convent to repent of her sins. He cannot forget the pull of her famous beauty, and becomes confused about the values of life. Later, as she is dying and can only see heaven opening before her, he comes to her side and tells her that her faith is an illusion, and that he loves her.