Cora is an idealistic and passionate teenager. Her absolute quest runs headlong into her parents misunderstanding and makes her flee her contemporaries. An essay on hypnosis that falls into her hands by chance, will become her tutor, her spiritual guide. She throws herself into the study of this "science," from which she expects miracles, and practices with a certain success her new powers of suggestion on all comers. Her meeting with Katz, "the king of hypnosis,' will be determinant and will make Cora move to the other side of the mirror.