Following the death of Isabel la Católica in the early 16th century, her widower Fernando de Aragón enters into an open war with his tyrannical son-in-law, Felipe el Hermoso, lord of Flanders, who wants to be the new king of Castilla above all.
In the middle of the conflict his wife Juana, Fernando's daughter, becomes the center of attention because of her unstable state of mind.
Trying to preserve the kingdom for their descendants, Fernando asks help from Cardinal Cisneros to make a deal with Felipe, who has his own agenda looking to expel Fernando from Castilla to claim the throne for himself, avoiding any contact between father and daughter that could be an obstacle for his ambitions.
But can Juana mediate between the two men in her life to prevent a war between the kingdoms that it annihilates the legacy and will of her beloved deceased mother, or will her growing insanity be the perfect excuse to start the war?