For seven years, the valiant Christian king Charlemagne has made war against the Saracens in Spain. Only one Moslem stronghold remains, the city of Saragossa, under the rule of King Marsile and Queen Bramimonde. Marsile, certain that defeat is inevitable, hatches a plot to rid Spain of Charlemagne. He will promise to be Charlemagne's vassal and a Christian convert in exchange for Charlemagne's departure. But once Charlemagne is back in France, Marsile will renege on his promises. Charlemagne and his vassals, weary of the long war, receive Marsile's messengers and try to choose an envoy to negotiate at Marsile's court on Charlemagne's behalf.
Roland, a courageous knight and Charlemagne's right-hand man, nominates his stepfather, Ganelon. Ganelon is enraged, thinking that Roland has nominated him for this dangerous mission in an attempt to be rid of him for good. Ganelon has long been jealous of Roland, and on his diplomatic mission he plots with the pagans, telling them that they could ambush Charlemagne's rearguard as Charlemagne leaves Spain. Roland will undoubtedly lead the rearguard, and Ganelon promises that with Roland dead Charlemagne will lose the will to fight.
After Ganelon returns with assurances of Marsile's good faith, Roland, as he predicted, ends up leading the rearguard. The twelve peers, Charlemagne's greatest and most beloved vassals, go with him. Among them is Oliver, a wise and prudent man and Roland's best friend. Also in the rearguard is the fiery Archbishop Turin, a clergymen who also is a great warrior. At the pass of Rencesvals, the twenty thousand Christians of the rearguard are ambushed by a vastly superior force, numbering in the hundreds of thousands. Oliver counsels Roland to blow his oliphant horn, to call back Charlemagne's main force, but Roland refuses. The Franks fight valiantly, but in the end they are killed to the man. Roland blows his oliphant so that Charlemagne will return and avenge them. His temples burst from the force required, and he dies soon afterward. He dies facing the enemy's land, and his soul is escorted to heaven by saints and angels.
Charlemagne arrives, and he and his men are overwhelmed with grief at the sight of the massacre. He pursues the pagan force, aided by a miracle of God: the sun is held in place in the sky, so that the enemy will not have cover of night. The Franks push the Saracens into the river Ebro, where those who are not chopped to pieces are drowned.
Marsile has escaped and returned to Saragossa, where the remaining Saracens are plunged into despair by their losses. But Baligant, the incredibly powerful emir of Babylon, has arrived to help his vassal. The emir goes to Rencesvals, where the Franks are mourning and burying their dead. There is a terrible battle, climaxing with a one-on-one clash between Baligant and Charlemagne. With a touch of divine aid, Charlemagne slays Baligant, and the Saracens retreat. The Franks take Saragossa, where the destroy all Jewish and Moslem religious items and force the conversion of everyone in the city, with the exception of Queen Bramimonde. Charlemagne wants her to come to Christ of her own accord. With her captive, the Franks return to their capitol, Aix.
Ganelon is put on trial for treason. Pinabel, Ganelon's kinsman and a gifted speaker, nearly sways the jury to let Ganelon go. But Thierry, a brave but physically unimposing knight, says that Ganelon's revenge should not have been taken against a man in Charlemagne's serve: that constitutes treason. To decide the matter, Pinabel and Thierry fight. Though Pinabel is by far the stronger man, God intervenes and Thierry triumphs. The Franks draw and quarter Ganelon (tie each limb to one of four horses running in opposite directions, which tears the victim to pieces). They also hang thirty of his kinsmen.
Charlemagne announces to all that Bramimonde has decided to become a Christian. Her baptism is celebrated, and all seems well.
But that night, the angel Gabriel comes to Charlemagne in a dream, and tells him that he must depart for a new war against the pagans. Weary and weeping, but fully obedient to God, Charlemagne prepares for yet another bloody war.