Born amid her parents’ ruthless struggle to unify and strengthen their kingdom, Juana of Castile (the third child of Queen Isabel and King Ferdinand of Spai), at the age of sixteen, is sent to wed Philip, heir to the Habsburg Empire. Juana finds unexpected love and passion with her dashing young husband, and at first she is content with her children and her married life. But when tragedy strikes and she becomes heir to the Spanish throne, Juana finds herself plunged into a battle for power against her husband that grows to involve the major monarchs of Europe. Besieged by foes on all sides, Juana vows to secure her crown and save Spain from ruin, even if it costs her everything.