Aang and friends arrive in the Earth Kingdom to begin his earthbending training, but a local general convinces Aang that all he needs to do is learn to control his Avatar state. Azula, Zuko's sister, arrives to escort her brother and uncle back to the Fire Nation.

On their way to Omashu, Team Avatar is forced to travel underground to avoid Fire Nation attacks. Iroh and Zuko adjust to life as fugitives.

Finding the city of Aang's old friend, King Bumi, captured by the Fire Nation, the heroes hatch a plan to rescue Aang's earthbending teacher. Azula gathers two old friends to help her hunt the Avatar.

Aang hears a swamp calling to him. In the swamp, Aang and the gang find out that this is not any natural swamp.

Sokka and Katara have to solve a centuries-old crime when Aang is imprisoned for a murder allegedly committed by one of his past incarnations.

While looking for an Earthbending teacher, Aang, and his friends discover a young blind girl with secrets of her own.

As Zuko tries to make it by in exile without his uncle, he remembers how his father became Firelord and what happened to his mother.

Team Avatar is getting chased by a mysterious machine, they become sleep deprived when they try to get away from Azula and her two friends. Katara and Toph get into a heated argument, she calls the earth bender out on her unhelpful attitude. Aang realizes the reason why they are being followed by the crown princess and her friends is because of Appa's shedding. Aang and his friends finally clean Appa up and he tries to create a fake decoy trail with the fur to trick Azula and her friends. Aang is finally cornered by the princess, she reveals that she is the younger sister of Zuko. Katara, Toph, Sokka, Iroh, and Zuko arrive to stop Azula, but she pretends to surrender to Aang and everyone else, she shoots lighting at Iroh as a distraction. Katara tries to help Iroh, but Zuko angrily rejects her offer. Team Avatar begins to part ways with Zuko and Iroh, the four friends finally gets some well-deserved sleep after being chased by Azula all day.

Aang begins to learn earthbending from Toph; Uncle Iroh resumes teaching Zuko firebending to better prepare him for facing Azula, and reveals a new technique he learned from watching waterbenders.

When he learns that there is a lost Library with all the knowledge in the world, Sokka convinces the others to seek it out in hopes of finding a weakness of the Fire Nation.

Lost in the desert without Appa, Team Avatar must find a way out. Iroh and Zuko make contact with a secret organization.

After getting tickets for the ferry headed to Ba Sing Se, the gang meets an old friend. They skip the ferry ride to help some refugees, one of which is going to have a baby, get to Ba Sing Se. They must lead the refugees through the Serpent's Pass, a dangerous mountain-side path surrounded by water.

After arriving at the great wall of Ba Sing Se, Aang and the gang discover that the Fire Nation has constructed a great drilling machine to penetrate the wall. The drill is also followed by an army of Fire Nation troops. Also, Zuko and Iroh are having trouble hiding the fact that they are both Firebenders.

After getting a house to stay in, Aang and company are given a tour of Ba Sing Se. As they try to get in to tell the Earth King the news, they find that nothing is quite what is seems. Jet is in the city, too, and he is positive that Iroh and Zuko are Firebenders.

A series of short stories covering some of the time spent by Katara, Toph, Iroh, Sokka, Aang, Zuko and Momo as they live in Ba Sing Se.

In this special episode, we go back in time to the moment Appa was stolen, will find out where he has gone and who he has met along the way and more importantly where he is now!

The Avatar gang encounters Jet in Ba Sing Se and he helps them to discover the location of Appa. But they will end up discovering something else, a secret of the city.

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.

Aang receives guidance from Guru Pathik at the Eastern Air Temple; Sokka is reunited with his long-lost father; Princess Azula has something diabolical in store for her enemies; Uncle and Zuko run their own tea shop.

The heroes work together to stop Azula's destructive plans; Zuko finds companionship in an unlikely source and learns the time has come to make an imperative choice about his future.