Ben Yusuf launches a bold invasion into the Muslim Taifa of Zaragoza, signaling the start of a broader push to seize the entire Iberian Peninsula. In response, the young prince Al-Mu'tamin flees to Castile to warn King Ferdinand about Yusuf's advance.
In Castile, Rodrigo Díaz de Vivar is described as living a life of privilege as the son of Don Diego Laínez de Vivar, a commander in Ferdinand's forces. He grows up at court with his best friend Sancho, who is destined to be the future king of Castile, and he harbors a forbidden romance with Jimena, the daughter of count Gormaz. The elder Gormaz disapproves of their relationship and tries to steer Jimena toward the arrogant Ordoñez.
When news arrives that the Almoravids from Zaragoza have crossed the border, Rodrigo joins Sancho, Ordoñez, and Gormaz on a scouting expedition near the frontier. After they set up camp, Gormaz is ambushed by Al-Mu'tamin and his men, but Rodrigo intervenes to defend his companions. In a surprising turn, Al-Mu'tamin speaks and is allowed by Sancho to accompany them back to Castile.
Time passes and the kingdom loses its ruler: Ferdinand dies. The cunning and jealous princess Urraca schemes to remove Sancho so her brother Alfonso can ascend the throne. One night, on Jimena's appeal, Gormaz and Rodrigo meet on a balcony where Rodrigo asks for Jimena's hand in marriage. Gormaz believes Rodrigo intends to replace him as commander and refuses; he even challenges Rodrigo to a duel. The duel erupts, while Urraca deploys her lover to strike Sancho down with a dagger. In the chaos, Rodrigo accidentally kills Gormaz. Jimena, witnessing the tragedy, is shattered and drives Rodrigo away.
Alfonso is crowned, and Rodrigo refuses to bow to him. He challenges Alfonso to swear that he had no part in his brother's death. Alfonso complies but, furious and humiliated, banishes Rodrigo.
Rodrigo then flees to Zaragoza, where his friends Álvar Fáñez and Garcés join him, along with Al-Mu'tamin. On Al-Mu'tamin's suggestion, the group plans to retake the castle of Emir Al-Muqtadir of Zaragoza. With Garcés' adopted badger, Ruidoso, they infiltrate the fortress and free Al-Muqtadir and other enslaved Muslims. Rodrigo is named commander of Al-Muqtadir's forces and begins reclaiming castles and lands that Yusuf had seized in the name of Alfonso, seeking to restore his own honor. He earns a new title among the Muslims: El Cid.
A new letter from Alfonso summons Rodrigo back to Castile. He returns alone to face the king, who explains that Yusuf has been gathering his army in northern Spain and offers a pardon if Rodrigo aids him. Rodrigo objects, warning that Yusuf intends to seize Valencia. Enraged by his defiance, Alfonso imprisons him. Urraca appears in Rodrigo's cell and tries to seduce him, but he resists. She then gives him the very dagger used in Sancho's murder and releases him, with the sly condition that he kill Alfonso.
Rodrigo confronts Alfonso in the royal chamber and instead reveals Urraca's plot, brandishing the dagger as proof. Startled, Alfonso frees him to leave. He stops by Jimena's room, but she has already turned away, convinced that Rodrigo killed her father. She refuses him, and Rodrigo, heartbroken, departs Castile.
Back in court, Alfonso brings Don Diego to the stand and presses him for answers about Rodrigo's fate. Diego denies freeing Rodrigo, claiming he was away at the time Rodrigo escaped. This strengthens Alfonso's suspicion that Urraca had facilitated Rodrigo's escape and Sancho's death. Urraca is arrested as Alfonso shifts to unite with Rodrigo's cause. Jimena, meanwhile, begins to reassess her loyalties and travels to Valencia with Rodrigo, though Ordoñez pursues them. They are captured by the Emir Al-Qadir, an ally of Yusuf.
Rodrigo and his companions stage a daring infiltration of Yusuf's fortress in Zaragoza, hoping to open the gates for a siege. The plan falters when Yusuf threatens Jimena, forcing Rodrigo to surrender. Garcés nevertheless helps them escape, and the fortress gates swing open for Rodrigo's troops, now led by Al-Mu'tamin. Yet Yusuf's forces quickly overpower the attackers, and Rodrigo faces Yusuf in single combat. Yusuf wins the exchange by disarming Rodrigo, while Ordoñez and Jimena make their escape. In a decisive turn, Alfonso's forces arrive to crush Yusuf's army. Yusuf makes a last effort to kill Rodrigo, but Jimena intervenes, reclaiming Yusuf's sword and enabling Rodrigo to disarm and finally defeat him.
With Yusuf’s defeat, Alfonso pardons Rodrigo and blesses his marriage to Jimena, while Ordoñez accepts the arrangement. The three march toward Valencia, where Rodrigo is granted dominion and begins a new chapter as a ruler who has earned his honor and secured a future with Jimena.
