From Appa to Azula, the city of Ba Sing Se holds something for everyone. But Aang, Katara, Sokka, and Toph are more than just tourists. Together they must stop Azula's treacherous takeover of the city or watch the Earth Kingdom fall to the Fire Nation. It all culminates in the best bending battle of the season!

Episode Descriptions:
Volume 4, Chapter 16
Following Appa's disappearance in Book 2: Earth, Chapter 10, Appa is taken by the Sandbenders from the library and sold to the Bedouins. Although Appa is tied down, he is hard to control so the Bedouins sell Appa to a traveling Fire Nation circus. At the circus, a cruel animal trainer "breaks" Appa and forces him to perform in the circus. Appa manages to break free from the circus and goes searching for Aang. Unable to find him, he looks for a place to rest. Appa finds shelter in a barn, but he is violently chased away by a farmer. Still looking for shelter, Appa finds a cave but realizes that the cave is home to another animal a Boar-q-pine. The two animals have a vicious fight and Appa is injured, stuck with Boar-q-needles. Appa is now becoming more animalistic and it shows when Suki (from Book 1 Chapter 4) comes across him. Appa is like an angry beast and Suki has to calm him down. She and the other Kyoshi warriors take care of Appa but it doesn't last for long the Kyoshi warriors are attacked by Azula, Mai and Ty Lee -- and Appa is forced to flee.

Volume 4, Chapter 17
Aang is searching around Ba Sing Se for Appa. He is lead off track by the Dai Li and Long Feng, who actually have Appa and who don't want Aang to find him. The kids run into Jet who has been brainwashed by the Dai Li. He has information on a secret underground prison. Could this be where Appa is? The kids try to deprogram Jet so that they can get the information about the prison from him. Meanwhile, Zuko finds out that Aang is in the city and decides that he is going to find the bison first. So the race to find Appa has begun!

Volume 4, Chapter 18
After a joyful reunion with Appa, the kids are determined to visit the king to tell him of the conspiracy taking place in his city.

Upon arriving at the palace, the kids realize Long Feng and the Dai Li have been expecting them. With Toph's help, they plow through and eventually find the king in his chambers, completely insulated, even from the ruckus going on in his palace. They spill everything to the king. He listens in disbelief as they tell him of the war going on, of the Fire Nation drill, and of the massive Dai Li conspiracy. He can't believe his eyes. "What is the Fire Nation doing at Ba Sing Se?" The kids tell him it's because they're about to invade his city. Long Feng protests, and the king has him arrested.

As the king's men scour through what remains of the Dai Li offices, they find even more incriminating evidence of several important messages that Long Feng has intercepted. There is a letter to Toph from her mother, who is apparently in the city trying to find her. And there is also a letter from the Water Tribe platoon written by Katara and Sokka's father! In addition, Aang finds a message attached to Appa. It's from a guru at the Eastern Air Temple. This mysterious stranger claims to have helpful advice for Aang.

In a moment of tension, the kids realize they must separate in order to fulfill their individual needs.

Volume 4, Chapter 19
Without their friends to bail them out, each of our heroes must discover and rely on their own inner strengths to solve their individual dilemmas.

Aang arrives at the Eastern Air Temple with Appa and meets the Guru. He is delighted to finally meet the Avatar. He places his hand on Aang's arrow and says, "You are an emotional time bomb. If you do not deal with your inner turmoil and gain control of the Avatar state, you will become the most destructive force in the world."

Sokka reunites with his father, Bato, and the men of his tribe. Hakoda is shocked to see his son again, and can't believe how much he's grown. He updates Sokka on their mission: for several months, the Water Tribe has been protecting the mouth of the bay (or river) from Fire Nation ships. If the ships get through, the Fire Nation could launch a naval assault on Ba Sing Se.

Toph is in a metal box, being transported back home, by Xin Fu and Master Yu. The two men remark on how wealthy they will be once they return Toph to her father. When Toph realizes that her charm isn't going to get her out of the box, she decides to bend her way out. Focusing her chi, Toph tries to bend the small particles of earth that are present in the metal.

Katara arrives at the King's palace, eager to greet Suki and the Kyoshi warriors. But as the girls turn around, Katara realizes something is wrong but before she can react, Ty Lee attacks Katara, taking away her bending. Katara is now Azula's prisoner.

Volume 4, Chapter 20
As Aang and Sokka fly back toward Ba Sing Se, it's clear that Aang is really shaken up. Sokka asks what kind of trouble Katara is in. Aang says he doesn't know exactly what's wrong but in his vision, she called to him for help.

Azula has taken over the Dai Li and subjugated Long Feng to her will. Now she has plans for the entire Earth Kingdom. She orders that Katara be taken to a secret place. She is betting that the Avatar will be stupid enough to focus on saving his friend instead of saving the city.

The gang meets with the Earth King. Despite Aang's concern, the Earth King claims everything is going fine, and Katara is fine. It's not long before Azula captures the King, Sokka, and Toph.

Zuko, also Azula's prisoner, and Katara are placed in a crystal prison chamber with no apparent way to get in or out. They two begin opening up to each other -- just a little. Katara discovers that Zuko is more honorable than she thought. She offers, if only momentarily, to heal Zuko's scar.

But Zuko is not to be trusted. In a dramatic, season finale battle, he and Azula team up against Aang and Katara in the crystal chamber. The battle is fierce and evenly matched. Zuko announces, "It's over, Avatar... capturing you has always been my destiny." Aang responds, "You've got your destiny... and I've got mine." His eyes and tattoos begin glowing. But just as his powerful form rises heroically, Azula zaps him with a particularly forceful bolt of lightning. Aang falls, mortally wounded. Katara rushes to his side. She is able to get him to safety thanks to last minute cover from Uncle Iroh.

Azula relishes their victory, and assures Zuko that he did the right thing. When he returns to the Fire Nation father will welcome him as a returning war hero. But Zuko's expression shows he is not sure if he made the right choice.

Bonus Materials:
- Free* exclusive Avatar comic book inside
- *With DVD purchase. While Supplies Last.
- Audio Commentary by Creators, Cast & Crew