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.

Cabrera convinces the King to receive Isabel and Fernando in Segovia. Away from the Court, Pacheco offers Queen Juana his support while he plots to kidnap Isabel and her daughter.

Reconciled, Fernando and a pregnant Isabel face their biggest test yet as the Portuguese invade Castile. King Alfonso marries Juana to reinforce her claim, but is reluctant to consummate the marriage as his supporters insist him to.