While on their way to the North Pole, Aang and his friends arrive at a giant canyon where two groups of refugees are bickering over who should get to go across. Aang decides to walk across with the two groups to ensure they don’t fight one another. However, he soon learns that the two tribes have been feuding for one hundred years and they both believe their actions are justified. But when the predators inside the canyon start to come out, Aang is stuck trying to defend both tribes from each other and the vicious wildlife.

Aang and the gang discover an Earth town that celebrates something called "Avatar Day." But when they get there and learn the festival is of "anti-Avatar" sentiment and Aang is put on trial for a crime a past incarnation allegedly committed. Looking to clear the Avatar's good name, Katara and Sokka venture back to a familiar place to gather evidence and discover the truth.

A mysterious tornado pulls the kids into a supernatural swamp where Katara, Sokka and Aang have mysterious visions. Meanwhile, Momo and Appa are chased by rogue swamp dwellers and only Aang and the gang can save them.

While traveling towards the North Pole, the group almost gets captured by the Fire Nation. However, when a charismatic young man and his band of rebels attack the Fire Nation camp and rescue them, they learn that they are trying to resist the Fire Nation’s motives to expand their territory. Katara and Aang really enjoy their time with the band of rebels, but Sokka soon discovers that they aren’t as noble as meets the eye.

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.

When the group tries to help a man who is being attacked by a platypus-bear, they discover that the local town has a fortuneteller named Aunt Wu in it, who has been forecasting the town's fate for years. But when Sokka and Aang discover one of the fortuneteller's most vital predictions is dead wrong, they have to develop a plan to convince the stubborn townspeople that their beloved Aunt Wu was wrong.

Aang feels neglected as Katara and Sokka reunite with Bato, an old friend of their father’s from the South Pole. They begin to reminisce on their times in the past while they wait for a message to arrive from their father. Aang believes Katara and Sokka will abandon him and go out to find their father should the message arrive. However, when the messenger gives Aang the message to give to Bato, Aang betrays his friends in a way Katara or Sokka could never imagine. However, when Zuko recruits a bounty hunter named June to track Aang down, his friendship is put to the test as he must deal with the fact that he betrayed his friends while defending himself from yet another fight.

In a nearby Earth Village, the gang meets a teenage earthbender named Haru. This village lives in fear of the Fire Nation, for soldiers there capture any earthbenders they can find.

After Katara attempts to teach Aang waterbending, but realizes that he is learning it much faster than she is, she is desperate to improve her abilities. When Katara inadvertently stumbles across a waterbending scroll that can help improve her abilities at a pirate’s store, she decides to steal it, realizing that she couldn’t hope to afford it.

When Aang and his friends hear rumors about surviving airbenders, they decide to stop by the Northern Air Temple on their way to the North Pole to see for themselves. What they find is a bunch of people who are not airbenders, but have mastered the art of gliding; though this upsets Aang because they have been defacing the temple. However, there was one part of the temple where nobody has been able to enter, and what Aang and his friends discover inside spells oncoming conflict.

When the gang arrives at a suffering fishing village, a mysterious spirit appears to help the villagers.

Two teenage siblings (Sokka and Katara) living in the South Pole discover a very strange boy (Aang), along with his pet flying bison Appa, in an iceberg. But can they trust him when he accidentally draws the war to their village's doorstep?

The gang arrives at Kyoshi Island and are captured by some Kyoshi warriors. When Aang reveals that he is the avatar, news quickly spreads out, eventually reaching Zuko, who then goes to Kyoshi Island to capture him.

Aang's abilities as an airbender are challenged by a king.

Aang and friends visit a village being terrorized by an angry spirit. Iroh is captured by Earth Kingdom soldiers.

Katara and Sokka discover that Aang is the long-lost Avatar and must rescue him when a Firebending prince named Zuko kidnaps him.

On their way to Omashu, Aang, Katara, and Sokka meet a group of nomads who show them a shortcut through the "Cave of Two Lovers". But when the group becomes trapped in the cave, it's up to Aang and Katara to save the group by trusting in love, possibly questioning their relationship. Meanwhile, Iroh gets a lethal rash so Zuko and Iroh head to a small Earth Kingdom town for help, hoping their real identities will not be discovered.

When Katara expresses her disapproval of 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, they are left vulnerable and are forced to face the dire consequences.

Despite the shocking news the gang have just discovered, Aang insists on trying to find King Bumi within Omashu's borders, even with the dangers that will await him and his friends if his real identity is discovered. Meanwhile Azula goes in search of old friends to help her with her mission.

When Aang and the gang meet up with a group of refugees, they tell the gang where they can get on a ferry to Ba Sing Se. But after a series of events they have to take a deadly route called the serpent's pass with the help of an old friend, Suki. Meanwhile Zuko and Iroh meet up with a boy named Jet and his freedom fighters.

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.

Aang is excited about going home for the first time in one hundred years, but he is shocked to find out that the temple is deserted. Aang tells Sokka and Katara about his childhood as they explore the temple, but they soon discover something that Aang never expected. Meanwhile, Zuko must make repairs to his ship and the only way he can do it is to dock his ship at his rival's naval base.

Aang and his friends go to a Fire Nation town so that Aang can witness some firebending, but their plan soon goes awry when it’s discovered that he is the Avatar. Fortunately, he's rescued by an individual who serves a firebending master named Jeong Jeong who has abandoned the Fire Nation, so Aang decides to use this time to attempt to learn firebending. The firebending master, however, seems reluctant to teach Aang.

Toph's instructing abilities come into question when Aang cannot seem to overcome a block that keeps him from earthbending. Sokka gets himself in a jam, while befriending what was, moments before, his next meal, and Iroh and Zuko begin training utilizing new philosophies and methods that originate from the other elements.

The kids battle Long Feng and the Dai Li when they attempt to show the Earth King the vast conspiracy taking place in his city. Zuko becomes seriously ill and has feverish dreams as he faces a spiritual crisis.