Isabel and Enrique debate peace terms at Guisando. King Juan II of Aragon, seeking Castilian support against France, sends his emissary Peralta to negotiate the marriage of his heir Fernando - to Juan Pacheco's daughter.

Isabel debates her marriage options. Her supporters want her to marry Fernando, and Enrique, the King of France's brother. Pacheco and the King count as an advantage that the devout princess won't lie to them.

Isabel and Fernando marry in Valladolid with the support of several nobles and are acclaimed by the people. However they are cousins and the marriage needs a Papal bull to be valid.

Isabel visits Seville, Castile's richest city but also a place plagued by crime and corruption. Juan II accuses Fernando of caring more for his wife's kingdom than for his. A border incident sours relations between Castile and Granada.