In medieval Europe, the tenth child of a family is traditionally destined for the Church. Hildegard is 11 years old in the fall of the year 1115 when her parents send her to the abbey of St. Disibod in the Rhineland to become a novice. She is excited for her new life because abbeys run schools, and Hildegard wants to become a physician.
However, once at the convent, Hildegard realizes that she is expected to live in seclusion with three other nuns, including their ascetic superior, Sister Jutta, the convent’s founder. Hildegard becomes homesick, longs to go to school, and her disappointment and unhappiness are growing. One night she discovers Jutta’s secret practice of mortifying her flesh with a whip, and she becomes ill. Hildegard is taken to the infirmary where the kindly Brother Wigbert takes care of her, and after she recuperates he takes her on as his assistant, despite vehement opposition from Prior Helenger.
Under the new arrangement, Hildegard begins to learn about medicine from Brother Wigbert, who also teaches her to read using ancient texts from the abbey library. One day, when she is alone in the herb garden, Hildegard discovers a breach in the abbey wall and sneaks outside and runs through the forest, feeling free and happy again. In the forest she encounters a boy named Volmar who is also a novice at St Disibod. They begin taking secret trips, and develop a fast friendship.
As Hildegard grows up, her reputation as a healer spreads, and she begins to write about herbs and medicine. When their novitiate comes to an end, Volmar confesses his love for Hildegard and although she shares his feelings she decides, after a great deal of internal struggle, to take her vows because the monastic path is the only way for a woman to be able to practice medicine. The day after her veiling ceremony, Volmar leaves the abbey.
When Sister Jutta dies, Hildegard is elected superior of the convent. She soon discovers that Jutta had been ceding the sisters’ dowries to the monks for years, and the convent has no money. She admits a beautiful and wealthy novice Ricardis and refuses to hand over her dowry, which elicits further hostility from the monks. Hildegard grows close with Ricardis who has a talent for drawing, and subsequently becomes the illuminator of Hildegard’s manuscripts.
Volmar returns to St Disibod. He became a Benedictine monk in France and begins to work as a scribe in the scriptorium, where he edits and copies Hildegard’s writing. Ricardis and Volmar become Hildegard’s closest collaborators, and Hildegard confides in them that she wants to relocate the convent due to the growing persecution from the prior.
On the anniversary of Jutta’s death, Hildegard visits her grave and vows to leave the abbey, but unbeknownst to her Ricardis is about to betray her and reveal her plans to the monks. She will now have to find an ally beyond the walls of St. Disibod to save her community, and to safeguard her future as a writer and physician.