Isabel's decision to take the Crown while Fernando is in Aragon angers him, a division that Carrillo is eager to use. Meanwhile, Diego Pacheco seeks support from Portugal and the nobles to dethrone Isabel in favor of Juana.

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.

Fernando besieges Burgos while the Portuguese try to send a relief column to the rebels. Meanwhile, Isabel balances the conflicting interests of the Aristocracy, the Church and the Jews to finance the war.

Isabel debates showing mercy to the rebels when the new bread tax causes an uprising in Segovia. Chacón ponders retirement. Juana feels imprisoned during her husband's absence and seeks solace in her stepson, the Prince of Portugal.

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.

The King's long absence throws Portugal in confusion, but Isabel and Fernando are no less divided over their next move. Rome pressures Castile to adopt the Inquisition. In Granada, the jealous Aixa plots against the Emir.

The converts of Seville look at their options in the face of the Inquisition. Juana's unruliness threatens the peace between Portugal and Castile. Beatriz learns her nephew's secret. Muley-Hacén names his heir.

It's time to visit Aragon to nominate Prince Juan as heir to the kingdom, but this is the least of Isabel and Fernando's problems. Granada invades Zahara, Catalonia is divided and the royals must face their most dangerous pregnancy yet.

The war bogs down as the nobles of Spain prefer to pursue their own interests before the Crown's, but a stroke of luck might tip the balance in the fight between Christians and Muslims. In Portugal, the king seeks to reinforce his position.

Fernando makes his authority in Aragon clear. Isabel receives a foreign sailor with a bold proposal. El Zagal rallies all Muslims to make common front against the Christians.

Fernando lays siege to Malaga, El Zagal's stronghold and richest city in Granada, while the Muslims appeal to their brethren outside Europe. Isabel receives the two queens of Granada.

Just as the Granada War nears its end, Prince Juan's sudden illness threatens to give Isabel and Fernando's kingdoms to the Portuguese. Columbus retouches his plan, and Torquemada investigates a murder.