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.

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.

While on the island, Aang seeks guidance from his past lives, but is not pleased with what he is told. The island, in fact, turns out to be a lion turtle from which Aang is given the guidance he had been seeking. After the tracker is unable to track Aang, the rest of the group decide they must find Iroh. Meanwhile, while tracking down Iroh, the group meets up with The Order of the White Lotus, a group that transcends the division of the four nations.

A play recounting the gang's adventures does not sit well with Aang and his friends, except for Toph who enjoys it very much. Meanwhile, Aang confesses his love to Katara, but the response is ambiguous.

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.

Zuko and Sokka make new plans to break out of the prison with Suki, Sokka's father and some others while a shocking twist leaves Azula none too happy with her two closest friends.

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.

While teaching Aang firebending, Zuko realizes that he has lost all his firebending skills. To regain his powers, Zuko and Aang must seek the original source of firebending within the ruins of a lost civilization.

Aang and the group arrive at the Western Air Temple, with Zuko in pursuit. Zuko wishes to help the Avatar end the war by teaching him firebending.

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.