

Book One: Water
One hundred years before the start of the series a twelve-year-old Airbender named Aang learns he is the new Avatar. Fearful of the heavy responsibilities and the separation from his beloved mentor Monk Gyatso, Aang flees from home on his animal guide, a giant six-legged flying bison named Appa. Caught in a fierce storm, they crash into the ocean, triggering Aang's protective Avatar State which freezes them in a state of suspended animation inside an iceberg. After his disappearance, Fire Lord Sozin, knowing that the new Avatar is an Air Nomad, launches a genocidal campaign against the Air Nomads in order to ensure his plots for world domination will not be interrupted by the Avatar. The Avatar is the only Air Nomad to survive the attack.
A hundred years later Katara, a fourteen-year-old Waterbender girl, and her older warrior brother, Sokka, free Aang and Appa from the iceberg. The three travel to the Northern Water Tribe so Aang and Katara can learn Waterbending. While on their journey, Aang and friends visit the Southern Air Temple where Aang discovers that the Fire Nation wiped out the Air Nomads. At the Southern Air Temple Aang meets his Avatar guide, Avatar Roku. The trio is constantly being pursued by banished Prince Zuko, the exiled son of Fire Lord Ozai, who can only return to the Fire Nation and reclaim his honor and throne if he captures the Avatar. Zuko travels with his uncle Iroh, a legendary Fire Nation general and the older brother of Ozai. Competing with Zuko for the Avatar is Admiral Zhao, who leads a Fire Nation assault on the Northern Water Tribe that is successfully repelled thanks to Aang and his friends. After the siege is ended, the Fire Lord tasks his daughter Azula to capture Zuko and Iroh, who are now considered traitors to the Fire Nation.
Book Two: Earth After leaving the North Pole, Aang masters Waterbending under Katara's tutelage. Searching for a new Earthbending teacher, the group meets Toph, a blind Earthbending prodigy who teaches Aang how to "see" using earthbending and vibrations. Meanwhile, Zuko and Iroh, now fugitives from the Fire Nation, attempt to lead new lives in the Earth Kingdom. Zuko, with the help of his uncle, tries to come to terms with his troubled past and his obsession with capturing the Avatar. Aang and his friends discover that an upcoming solar eclipse will deprive Firebenders of their bending, leaving them open to invasion and giving Aang his chance to defeat the Fire Lord. Azula and her two friends Mai and Ty Lee pursue Team Avatar, who struggle to reach Ba Sing Se, the Earth Kingdom capital, and tell the Earth King of the eclipse. After capturing and impersonating the Kyoshi Warriors, friends of Team Avatar, Azula persuades an elite group of Earthbenders called the Dai Li to instigate a coup d'etat, allowing the Fire Nation to capture Ba Sing Se. In a final confrontation, Zuko sides with his sister, who promises to restore his honor. Azula mortally wounds Aang, who is in the Avatar State, with a lightning blast. Iroh helps Aang and Katara to escape after Zuko betrays him, and is imprisoned by the Dai Li for his actions. Katara revives Aang with spirit water from the North Pole, but his seventh chakra is blocked and he cannot enter the Avatar State.
Book Three: Fire
Aang awakens to find the group disguised as Fire Nation soldiers heading West on a Fire Nation ship, while Zuko has been restored to his position as crown prince and Iroh is imprisoned as a traitor. Sokka has planned a small-scale invasion of the Fire Nation to capture the Fire Lord's palace and defeat Fire Lord Ozai, taking advantage of the solar eclipse. The invasion will be staged by a ragtag group of benders and warriors whom Aang has helped along his journey. Initially the invasion proceeds as planned, but Aang fails to find the Fire Lord before the eclipse ends. The invasion ultimately fails, and only Aang and the rest of the young ones are able to escape. Zuko, in a change of heart, decides to defy his father and join the Avatar. Zuko catches up with Aang at the Western Air Temple and offers to teach Aang Firebending. After some reluctance from Katara and Sokka, Team Avatar allows Zuko to join the group.
In the series finale, Aang and his friends confront the forces of Fire Lord Ozai, who plans to use the power of Sozin's Comet to destroy the other nations and rule the world as the Phoenix King. Iroh, who escaped from prison during the eclipse, leads the Order of the White Lotus to liberate Ba Sing Se. Sokka, Toph and Kyoshi Warrior Suki take down the Fire Nation's airships, preventing them from burning down the Earth Kingdom. Zuko and Katara take on Azula, the new Fire Lord and are able to defeat her due to her deteriorating mental state. Aang struggles against Ozai, since he is reluctant to take his life. However, Aang is able to reenter the Avatar State and ultimately defeats Ozai by taking away his firebending powers with a technique known as energy-bending, taught to him by an ancient lion-turtle. With Ozai defeated, the war quickly ends. Zuko is crowned the new Fire Lord and, with the help of the Avatar and his friends, begins rebuilding the four nations. The series ends as Aang and Katara kiss beneath the sunset.