The civil war in Castile comes to its most decisive point as the armies of Enrique and Alfonso face each other in Olmedo. In Segovia, the Queen prays for her husband and Isabel for her younger brother.

After their recent loss, Carrillo advices Isabel to continue the war and Chacón to seek peace. Enrique finds betrayal in a place he didn't expect. Chacón worries as Gonzalo and Isabel compare their feelings for each other.

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.

Fernando travels under disguise to meet Isabel in Valladolid, keeping an eye out for bandits and Pacheco's men. Isabel grows afraid as the time to sleep in the wedding bed comes near. Gonzalo can't hide his jealousy.

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.

King Juan convinces the new Pope to sign the bull authorizing Isabel and Fernando's marriage. Rome's envoy, Cardinal Borgia, also must propose a new Castilian cardinal - a position that Carrillo and Pedro Mendoza strive for.