Johanna (Johanna Wokalek) grows up in ninth-century Europe in Ingelheim am Rhein. The daughter of the dogmatic and doctrinaire village priest, she teaches herself to read and write in secret. When her extraordinary talent is discovered, she is allowed to attend the cathedral school in Dorstadt, where she falls in love with the knight Gerold. Following a bloody attack by Normans, Johanna disguises herself as a man and enters the monastery at Fulda. She learns the art of healing and is ordained. Her reputation as a healer takes her to Rome and she becomes the personal physician and confident of Pope Sergius (John Goodman). When the pope dies, she ascends the throne despite a brewing conspiracy. But the undiscovered "popess" has a dangerous weak point: she is pregnant by Gerold, her secret lover.