Aang awakens to find himself aboard a captured Fire Nation ship with a full head of hair and sustaining serious injuries from the previous battle for Ba Sing Se. At his side are Toph, Katara, Sokka, and their father Hakoda who recount the events that led the four to the ship and contemplate their next move. Aang struggles to fight his own desire to face the Fire Lord before he is ready. Meanwhile, the once exiled Prince Zuko deals with his own issues as he makes his long-awaited journey home, with the fear of his father's rejection hanging over his head.

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 while at the same 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 his imprisoned uncle.

When the gang arrives at a suffering fishing village, a mysterious spirit appears to help the villagers. Aang decides to seek out the spirit for her help, but she may be more familiar then he thought. Can Aang solve the mystery of this cryptic spirit and help the town from the Fire Nation?

Feeling as though he isn't contributing enough to the group, Sokka seeks out an elusive swords master from whom he can learn the ways of the blade. But, Sokka soon has doubts whether or not he is worthy. Can Sokka pull himself together or will the gang lose an important team member and friend?

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. Arguments rise and fall. Will the group learn to become friends and trust each other? Elsewhere, Aang and others face off against a new adversary. What will this lead to?

The tale of Avatar Roku and Fire Lord Sozin is revealed to Aang and Zuko by different sources. Both learn about themselves and are shown the origins of the war. But will Zuko and Aang learn anything from this?

When Katara expresses her disapproval to Toph's new way to make quick cash, the group finds her too motherly, and tension grows between Katara and Toph. When Katara finally decides to participate in this scam to disprove Toph's accusations, the gang is left vulnerable and are forced to face dire consequences.

The gang meet a waterbender who lives in the Fire Nation after being captured years ago. Katara becomes her pupil to further develop her waterbending, while Aang, Sokka, and Toph discover she might be connected to a bunch of disappearances. So can this mysterious waterbender be trusted?

Four days prior the invasion, Aang becomes nervous over his soon-to-come confrontation with the Fire Lord. His anxiety gets the better of him as he begins to suffer from outrageous nightmares and hallucinations. Meanwhile, Zuko becomes upset to learn that he was not informed about a war meeting.

The day of the eclipse has arrived, and the invasion force gathers together to make last preparations. They infiltrate the island and the battle begins. Meanwhile, Aang searches for the Firelord.

As the invasion force fights their way to the Fire Nation capital, the kids help Aang to find the Fire Lord in time for the eclipse, but there are a few surprises waiting ahead. Will Aang finally complete his mission or will he lose the battle against the forces of the Fire Nation?

Aang and his group finally arrive at the Western Air Temple. There, they meet a repented Zuko, who offers to join their ranks. But acceptance of their former enemy's intention is not in their plans. Zuko has a hard time trying to earn everyone's trust, however, another unexpected encounter might change his chances.

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

Sokka is haunted by the decisions he made during the invasion plan, and feels the need to regain his honor. With the help of Zuko, Sokka travels to the highest security prison in the fire nation, The Boiling Rock. Disguised as guards, they search the prison, until one of them is revealed. With time running out, Sokka needs to decide if he should cut his losses and leave, or try to finish what he started.

Sokka has found his father, but with one escape plan failure, he doesn't know if there's another way off the island. Luckily, two water tribe minds are better than one, but can Sokka free his dad and his friends before Azula arrives?

Meanwhile, Zuko gets questioned and a visit from the one person he didn't want to leave.

Azula attacks the Western Air Temple, forcing the gang to flee. Meanwhile, Katara still doesn't trust Zuko. Zuko talks to Sokka, and confirms that he knows the person whohuged Katara's mom. When Zuko and Katara go off to find him, will Katara go too far when she does?

The gang, now hiding at Ember Island, finds out that there is a play about them and all their past adventures. Meanwhile, Aang tells Katara how he feels about her, but the response is ambiguous.

Aang begins having second thoughts on what to do when he comes across the Fire Lord. Zuko reveals the Fire Lords special plans for his victory over the Earth Kingdom. And just when everone gets ready to leave, Aang disappears...

After they can't find Aang, the group decides to find Iroh, who they believe is the only person other than Aang who can stop Fire Lord Ozai. Meanwhile, Aang consults his past lives for help in facing the Fire Lord.

The group splits up to end the war. Zuko and Katara head to the Fire Nation capital to deal with Azula; Suki, Sokka, and Toph attempt to thwart the Fire Nation's airship battalions, and Aang prepares for his confrontation with Phoenix King Ozai.

Aang unleashes the full power of his long-dormant Avatar State to fight back against the Fire Lord, but can he end his reign of destruction without taking his life? Can Sokka, Toph, and Suki escape the fallen airships? And can Katara defeat an unstable Azula in time to save Zuko's life? The final battle ends here!