To better blend in as Fire Nation citizens, Aang enrolls in a Fire Nation school, giving himself an opportunity to learn more about the Nation and to enjoy life as a normal kid for the first time since he discovered he was the Avatar. Meanwhile Zuko, growing more and more paranoid about the Avatar's false demise, brings himself to confront the imprisoned Iroh.

Zuko, Azula, Mai and Ty Lee take a vacation to Ember Island. In the process, they come to learn more about themselves and each other as well as their desires for the future. Elsewhere, Aang and the others face off against a new adversary.

The gang investigates the bizarre disappearances taking place within an eerie town.

As the invasion force fights their way to the Fire Nation capital, the kids help Aang find the Fire Lord in time for the eclipse. Zuko confronts his father with shocking news.

Sokka wants to break his father out of jail and asks Zuko for information on Fire Nation prisons. Sokka and Zuko head for the Boiling Rock, a prison located in the middle of a volcano, to rescue Sokka's father.

Katara decides to confront the Fire Nation soldier responsible for her mother's death. Aang tries to talk her out of it, but she doesn't listen.

Sokka, Suki, and Toph try to stop the Fire Nation's air fleet. Meanwhile, Zuko and Azula duel in an Agni Kai and Aang confronts the Fire Lord. On the verge of losing, Aang gets hit in the back of his scar which sends him into the Avatar State.

Aang defeats the Fire Lord by bending the elements within the Fire Lord and removing his firebending abilities. After Zuko is taken down protecting Katara from Azula, Katara joins the fight and manages to restrain Azula. Afterwards, Zuko is crowned Fire Lord and promises a better future for the world, while Aang takes his place as the next Avatar. Katara finally shows her love for Aang as they kiss under the setting sun.