They said goodbye and continued their journey. Meanwhile, Azula began hunting Zuko and Iroh. The kids reached an Earth Kingdom base where General Fong wanted to force Aang into the Avatar State so they could defeat the Fire Lord immediately. Katara strongly disagreed, but Aang agreed to try. Nothing worked. He could not enter the Avatar State. Meanwhile, Azula lied to Zuko and Iroh, saying that their father had forgiven them and wanted them home.
Iroh immediately suspected a trap, but Zuko insulted him. Back at the base, Aang ended the dangerous training, but General Fong attacked him. Aang did not want to fight, but when Katara was buried alive, he lost control, entered the Avatar State, and went on a rampage. Roku explained that the Avatar State gave him the power of every past Avatar, but that if he died in that form, the Avatar cycle would end forever. Aang calmed down and decided to continue his journey.
His next stop was Omashu, where Bumi was supposed to teach him earthbending. Meanwhile, when Zuko and Iroh met Azula, a soldier revealed that their trip home was actually an arrest. Azula planned to imprison them, not save them. They fought the soldiers and Azula. She nearly defeated Zuko until Iroh stepped in and knocked her aside. Zuko and Iroh cut off their royal topknots and threw them into the river, leaving their old lives behind.
While practicing waterbending, the group met a band of nomads who told them the story of two lovers connected by secret tunnels beneath the mountains. After running into Fire Nation soldiers, they followed the nomads through the tunnels to reach Omashu. Meanwhile, Zuko and Iroh headed toward the Earth Kingdom to escape Azula and met a girl named Song, who shared how the Fire Nation had destroyed her family.
Zuko was surprised when she revealed her own burn scar. Inside the tunnels, Sokka's plans failed because the passages constantly changed. The group got separated, and Aang and Katara found the lovers' tomb. Katara suggested kissing to find their way out, but Aang awkwardly rejected the idea and hurt her feelings. Later, lost in the darkness, they shared a quiet moment, and a glowing crystal path appeared before them, while Sokka and the others calmed the badgermoles with the nomads' music and escaped as well.
The group reunited and said goodbye to the nomads. They reached Omashu, but found it occupied by the Fire Nation. They snuck inside through the old delivery tunnels. When Earth Kingdom rebels attacked the governor's family, Aang saved the governor's baby, drawing the attention of Mai, a deadly knife thrower. The rebels rescued the kids and explained that Bumi had surrendered peacefully.
Meanwhile, Azula recruited Ty Lee, a talented acrobat, to join her team. Back in the city, the citizens faked a deadly disease called pentapox to escape. During the confusion, Momo accidentally ended up with the governor's baby, so the rebels arranged a trade: the baby for King Bumi. Azula arrived and recruited Mai to handle the exchange. Aang finally saw Bumi, but Azula changed the deal to no deal.
A huge battle began. Aang reached Bumi, but Bumi refused to leave and said that he could not teach Aang yet. Instead, Aang had to find a master who understood neutral jing, someone who waits, watches, and strikes at the perfect moment. Aang safely returned the baby, and the journey continued. The group arrived in another town looking for an earthbending teacher. They visited Master Yu's academy, but he only cared about money.
They heard about a secret underground earthbending tournament, and Katara tricked someone into revealing its location. At the tournament, they met the undefeated champion, Toph, a blind girl who fought perfectly by sensing vibrations through the ground. She was exactly the teacher Aang needed. Aang challenged her just to speak with her, but she refused. He accidentally won with airbending, making the promoter Xin Fu furious, because he thought the match had been fixed.
Aang learned that Toph was the daughter of the rich Beifong family. They visited her home to ask her to teach him, but she refused. And that night, Xin Fu's men kidnapped both Aang and Toph. Katara and Sokka paid Toph's ransom while the thugs planned to sell Aang to the Fire Nation, but Toph easily defeated every earthbender in the arena by herself.
Toph's parents were shocked to learn how powerful she really was. Knowing that they would only control her more, Toph ran away to become Aang's earthbending teacher. Believing that Aang had kidnapped her, Toph's father hired Xin Fu and Master Yu to bring her home. Zuko left Iroh to find his own path. He arrived in a poor Earth Kingdom village and protected a boy named Lee from corrupt soldiers.
Grateful, Lee's family gave him food and a place to stay. Zuko remembered his childhood. He had been very close to his mother, Ursa. Iroh had once been the heir to the throne and had given Zuko a knife from his campaign. Azula was always their father's favorite and was named after Fire Lord Azulon. While teaching Lee how to use the knife, Zuko smiled for the first time in a long while.
More memories returned. After Iroh lost his son Lu Ten, Ozai asked Azulon to make him the new heir. Angry, Azulon ordered Ozai to kill Zuko so that he would know the pain of losing his son. Soon after, Azulon mysteriously died and Ursa disappeared. Before leaving, she hugged Zuko and said, "No matter how much things change, never forget who you are." In the present, Zuko left the knife for Lee and rode away.
Soon, Lee's mother begged him to return, because the soldiers had taken Lee to force him into the army. Zuko came back and defeated the soldiers. Pushed to his limit, he remembered his mother's words, drew his swords, and revealed himself as Prince Zuko by using firebending. He saved Lee, but the villagers rejected him in fear. Zuko left alone across the desert.
The group set up camp while Appa shed his spring fur. Katara and Toph argued because Toph refused to help with camp chores. That night, a huge tank-like machine chased them. It followed them to every campsite, leaving everyone exhausted. They finally stopped running and discovered that Azula, Mai, and Ty Lee were hunting them. They escaped again, and Zuko also joined the chase.
The lack of sleep caused more arguments. Toph realized that the fur was leaving a trail. Katara blamed her for not helping, so Toph left the group. Aang washed Appa and left fake fur behind before reaching an abandoned town. Azula's team split up. Mai and Ty Lee fought Katara and Sokka, but Appa defeated them. Meanwhile, Toph met Iroh. They drank tea together, and she learned that it was okay to accept help.
She asked Iroh to tell Zuko that he needed him too. Azula found Aang, and Zuko arrived. The three fought until everyone surrounded Azula. She shot lightning at Iroh, seriously injuring him, and escaped. Katara tried to heal Iroh, but Zuko angrily forced everyone to leave. At last, the group finally got some rest. Later, Aang started learning earthbending from Toph, but it was much harder than the other elements, because he had to stand firm like a rock.
Meanwhile, Iroh recovered and taught Zuko how to redirect lightning. Aang struggled because earthbending was the opposite of airbending. Iroh told Zuko that understanding the other elements would help him, and that he had to face the conflict inside himself. Katara gave Aang the same advice. When Sokka went missing, the group searched for him and found him trapped. A wild animal attacked, but Aang finally stood his ground.
Toph declared him ready to learn earthbending, and he succeeded. Zuko climbed a mountain to practice lightning redirection, but instead he broke down crying. After so much training, the group took a short break. They stopped at a desert tavern and met Professor Zei, who was searching for a legendary library buried beneath the sand. When he said that it might contain Fire Nation secrets, they decided to help.
They found the library. Toph stayed outside with Appa while the others entered. The owl spirit Wan Shi Tong welcomed them, allowing them inside as long as they did not use the knowledge for war. While searching, Sokka discovered that soon a solar eclipse would completely remove the Fire Nation's firebending for a short time. It could end the war. Wan Shi Tong discovered their plan and attacked them.
They barely escaped. Outside, Toph revealed the worst news. Appa had been kidnapped. Aang lost his temper and decided to search for Appa alone, while the others struggled to cross the desert without water. Meanwhile, Iroh and Zuko returned to the same tavern, where Xin Fu and Master Yu tried to capture them for the reward. Iroh secretly contacted a member of the Order of the White Lotus through a Pai Sho game, and they escaped.
Aang rejoined the group, but he was still furious. They found a sand glider, but giant bees attacked them. Soon after, the sandbenders appeared. Meanwhile, Zuko and Iroh got fake passports to enter Ba Sing Se. Toph recognized the sandbenders as the ones who had kidnapped Appa. Aang entered the Avatar State and destroyed all their sand gliders. They admitted that Appa had been sold to merchants from Ba Sing Se.