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.

'The Cave of Two Lovers' is where we first see definite signs of the true nature of the growing love relationship between the main characters Avatar Aang and the water bending master Katara. Sokka is bombarded by a group of free-thinking hippie musical nomads during most of the episode as well making for many humorous moments of head-smacking good fun. Uncle Iroh and Prince Zuko learn about life on the run from the Fire Nation and how not to brew 'White Jade Lily' as a tea ever again. The history of how the Earth city of Omashu came into being is provided as well as a surprise ending about city's current state of being under the hand of the Fire Nation.

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.

Still searching for an earthbending teacher, Aang and his friends stumble across a small earth village. When they hear about an underground earthbending tournament, they decide to go to it. Aang finds a teacher that fits the description of King Bumi. Her name is Toph Beifong, a blind, 12 year old girl who is tougher than she looks. When they meet, Toph is at first reluctant, because her parents don't know how good of a bender she is. After her parents discover her secret life, she decides that she wants to join the Avatar gang to help him master earthbending.

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.

Everytime the land, Azula and her warriors find Aang, Katara, Sokka, and Toph. Toph refuses to help set up camp claiming she carries her own weight and no one else's. After a fight between Aang, Katara and Toph, Toph storms off angrily. Aang lays a decoy trail for Azula and Sokka, Katara, Appa, and MoMo, flee the other direction. Aang waits for Azula and is fighting her when Zuko and Iaro arrive. Soon, Katara, and Sokka come to the fight too. Just as all hope of winning is lost, Toph arrives and together, the six attack Azula. Knowing she is beat, Azula shots Iaro with lightning and disappears. Zuko leaves with Iaro and Aang, Katara, Sokk, and Toph leave as well. Toph and Katara apologize to each other and the journey continues.

Aang begins to learn earthbending from Toph; Uncle Iro 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. Iroh and Zuko make contact with a secret organization.

Aang, Katara, Sokka and Toph escape the library to face the desert without the benefit of Aang's flying bison, Appa. The group knows they must get the information they obtained from the library about the upcoming solar eclipse to earth kingdom capital of Bah Sing Se as it could very well make the difference in the ongoing war with the Fire Nation. Aang, who has always felt somewhat isolated by the realization that he is indeed the last air bender, considers Appa and Momo his only connections to his previous 100-year ago world. When Appa is stolen by sand benders Aang is visibly devastated and without direction or hope. Katara really shines in this episode as she must deal with Aang's despair, Sokka's cactus-induced hallucinations and Toph's lack of support or good ideas to solve their dilemma as she too feels they are just trapped in a 'giant bowl of sand pudding.' The highlight of this episode is when Aang finally confronts the sand benders who Toph recognizes as those who stole Appa. A showdown ensues and Sokka, Toph and the sand benders flee for their lives in fear of seeing Aang transform his rage and pain into the 'Avatar State.' Despite the apparent danger Katara remains in the whirlwind of sand unshaken. Again we see the growing 'understanding' between the Katara and Aang continue to develop. Katara trusts Aang enough to know he will not hurt her in the 'Avatar State' and Aang trusts Katara enough to let his defenses down to be vulnerable but only with her. Katara pulls Aang back and he returns sobbing quietly in her arms. Meanwhile Uncle Iroh and Prince Zuko successfully evade two groups seeking their capture as Fire Nation fugitives. Through Iroh's membership in the "Order of the White Lotus" they secure safe passage to Bah Sing Se to 'hide in plain sight' as refugees.

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 say. 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 army of fire nation troops. Also Zuko and Iro are having trouble hiding the fact that they are both fire benders.

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