As the only child of a successful merchant, Johanna has her wits and a sense for business.
The royal family is in deep trouble: ever since the crown princess died of illness, the king has attempted to educate his son to become king. However, the prince is "not good in the head" and quite unsuited to the task. In his grief for his daughter, the king has run the coffers dry: he hired dubious magicians for even more dubious tasks. Those magicians circle like vultures waiting for the kingdom to fail. The king must get his son on the throne, preferably supported by a smart and well-off wife.
He holds a ball in his son's honour. Johanna has agreed to a dance. But the guests include a number of magicians who are not there for the festivities.