Eldest recap

While the Varden mourn the death of their leader, Eragon and Saphira travel to the elven forest, where the hidden Rider Oromis and his dragon Glaedr train them in magic, lore, and combat. During an elven celebration, Eragon's crippling back wound is not only healed but his body is transformed, giving him elf-like grace and strength. Meanwhile his cousin Roran, hunted by the Empire, rallies their village to fight off soldiers and then leads the survivors on a hard journey to join the Varden, driven on because the king's servants have seized his beloved Katrina. Nasuada takes command of the Varden and moves them to ally with the land of Surda. The threads converge at the Battle of the Burning Plains, where Eragon faces a new enemy Rider on a red dragon. The rider is revealed to be Murtagh, alive and bound into Galbatorix's service, who claims that he and Eragon are both sons of the dead traitor Morzan and seizes Eragon's sword before departing.

In the first book, Eragon, a farm boy in a remote valley, found a blue stone that hatched into the dragon Saphira, making him the first new Dragon Rider in a generation. When the king's servants killed his uncle and burned his home, he fled with Brom, the village storyteller and a secret former Rider, who trained him in swordplay and magic before dying in an ambush. A guarded young man named Murtagh joined Eragon, and together they rescued a captive elf, Arya, and delivered her to the Varden, the rebels opposing King Galbatorix, at their hidden mountain stronghold. There an enemy army attacked, and Eragon destroyed the Shade Durza in battle, though he took a severe wound to his back. A hidden teacher then reached his mind and summoned him to the elves' forest to complete his training.

This second book opens in the aftermath of the great battle beneath the mountains. The Varden's leader has been lost, throwing the rebellion into uncertainty over who will command it and how the alliance of humans, dwarves, and elves will hold. Eragon, still troubled by the wound across his back, must soon set out for the elven forest to be trained as a Rider, while the wider war with the Empire looms and events back in his home valley begin to stir dangers of their own for the family and village he left behind.

The Battle of the Burning Plains brings every thread together. Nasuada, now leading the Varden in alliance with Surda, commits her forces against the Empire's army, and Eragon and Saphira, newly trained and physically transformed by elven magic, fight at the front. Roran, having saved his village and led its people across the land, arrives in time to join the battle and reunite with Eragon. A red dragon and its Rider appear on the enemy side and prove terrifyingly strong; when Eragon finally confronts the rider, the helmet comes off to reveal Murtagh, alive and forced into Galbatorix's service by oaths the king wrung from him. Murtagh tells Eragon that they are brothers, both sons of the king's dead servant Morzan, and, sparing Eragon, takes his sword Zar'roc and withdraws. The battle ends without a decisive victor. Eragon is left shaken by the claim about his parentage and by the loss of his blade, Roran resolves to march on to rescue Katrina, and the war grinds forward with the Varden's cause still hanging in the balance.