The gang arrives at the Great Divide, the world's largest canyon. Two Earth Kingdom tribes bicker with each other about how to cross the canyon, having been enemies for a century. Aang helps them cross the canyon together and is able to end the feud by fabricating a story about their ancestors.
Katara and Sokka are arguing over how to set up their campsite, with Aang ending the fight and gloating about his ability to solve problems as the Avatar. Soon after, they travel to the Great Divide, the largest canyon in the entire world. While Katara expresses awe at seeing the yawning chasm before them, Sokka is bored by the sight, viewing it as somewhat lackluster, and expresses his intent to fly over it on Appa. Before they can leave, however, a man runs up to them and warns them not to leave with a guide to cross the canyon because he was there first. The man angrily says to the team that he is holding a spot for the rest of his tribe, the Gan Jin, until they arrive. While waiting, the Zhang tribe arrives, whom the man claims has been an enemy of his tribe for a hundred years. The two tribes' differences are immediately visible: while the Gan Jin tribe appears neat, well-mannered, and clean, dressed in clothes of white fabric, the Zhang tribe seems dirty and primitive, dressed in garments made from animal skins. The earthbending canyon guide subsequently arrives, prompting both tribes to begin arguing over which should be escorted first: the Zhangs claim that some of their members are sick, while the Gan Jins assert that their elderly are weary from their travel. As the two tribes bicker, Katara wonders if Aang is ready to test his role as a mediator. Despite Aang's reservations about his possible success, Katara alerts the tribes of Aang's status as the Avatar, giving him the chance to propose that they all travel together. When the tribes dismiss the suggestion and resume their argument, Aang ends the verbal fight by shouting over the chaos that Appa will carry their sick and elderly while the two tribes cross the canyon together, conditions to which both tribes agree.
The canyon guide warns them not to take any food into the canyon, as food attracts dangerous predators in the canyon. The two tribes, the gang, and the guide begin their descent to the canyon floor. After the guide breaks a rock shelf so that potential Fire Nationsoldiers cannot follow them, a canyon crawler assaults them. Aang and his friends fend it off, but not before it attacks the guide, breaking both of his arms and rendering him unable to earthbend. With no other earthbenders in either of the groups, Aang realizes that they are now imprisoned in the canyon. Both tribes begin to argue again and finally decide to split up. As the tribes each blame the other for the attack, Aang furiously orders them to separate and travel in two separate groups. As they divide, Aang, curious as to why the two factions hold such animosity toward each other, asks Katara and Sokka to accompany the Gan Jins and the Zhangs, respectively, and try to discover the reason for their feud.
That night, both sides, unaware of the conversation of the other group, discuss the use of tarps; while the Zhangs feel it unnecessary to use them as rain protection during the dry season, the Gan Jins dutifully hang the tarps over their tents anyway, reasoning you could never be too careful. Their respective opinions cause Katara and Sokka to sympathize with the groups they are accompanying. Also around the same time, both tribes reveal that they brought food into the canyon against the orders of the guide, justifying their actions by stating that they should not go hungry while the other tribe, which they both believe to have brought food with them, eats. Both tribes soon tell their guests their version of the story behind their feud.
The Gan Jins tell Katara of their tribal forefather, an earthbender named Jin Wei, who was tasked with the job of taking the sacred crystal orb from a gate in the east to a gate in the west as part of a redemption ritual. They claim that, as he neared the western gate, Jin Wei was assaulted by a thief, a Zhang named Wei Jin, who stole the orb out of greed. The Zhangs, on the other hand, tell Sokka that their ancestor, Wei Jin, found Jin Wei passed out on the ground near the western gate. Wei Jin stopped to help the man and was told about the redemption ritual and the orb's importance. Rejecting assistance, Jin Wei asked Wei Jin to take the orb back to his tribe, which Wei Jin did. Upon arriving at the Gan Jin's village, however, Jin Wei's tribe arrested him for stealing the orb and imprisoned him for twenty years. Both sides claim that they will never forget the terrible injustice dealt to them by the other.
Aang spends the night with Momo and the guide, away from the tribes. When Aang sadly states that getting the two factions to cooperate is virtually impossible and that the most important issue before them is escaping the canyon, the guide wonders if the two problems are connected.
The next day, the two tribes reunite and reach the end of the canyon. When Aang asks Katara and Sokka if the tribes might work together at all, the siblings begin to argue, both siding with their assigned tribe. The tribes themselves also begin arguing again and when Aang tries to pacify them with his belief that "harsh words won't solve problems", both tribes prepare to fight in order to end the feud. Aang, angry, uses airbending to separate them; as the people tumble backward, the food they carried with them is discovered. Not believing what he is seeing, Aang scolds the tribes for disobeying the canyon guide's warning not to bring food, but is quickly distracted by an egg custard tart since he has not eaten in a day. As he speaks, a horde of canyon crawlers, attracted to the abundance of food, approach the refugees. After an initial skirmish with the beasts, Aang realizes that the crawlers want the food more than they want to attack the tribes and convinces the tribes to cooperate; by working together and throwing bags over the crawlers' heads, everyone is able to mount the beasts and, guiding them with food, ride them up the wall and out of the canyon.
Safe and out of danger, the two tribes pick up their feud where they left off and are on the verge of a physical altercation when Aang, upon hearing the names of the two tribes' ancestors for the first time, suddenly pipes up that he knew the two men personally long ago. He begins to tell everyone that he had met them a hundred years ago, though notes that a lot of confusion rose in regards to the details of the story. The men had not been enemies, but eight-year-old twin brothers, who played a game called "Redemption", clarifying that the sacred orb was the ball they played with and the gates the respective goals. As Jin Wei was running with the ball, he fell, fumbling the ball in the process; Wei Jin recovered it and started running to the other end of the field, though stepped out of bounds and was put in the penalty box for two minutes, not twenty years. He concludes his story by pointing out that while Wei Jin was "kind of a slob" and Jin Wei was "a little stuffy", they respected each other's differences enough to share the same playing field. Convinced by Aang's tale, the tribes make amends and continue their journey to Ba Sing Se, the Earth Kingdom capital, as one tribe, followed by the guide, who expresses his intention to never again return to the Great Divide.
As the tribes depart, Sokka tells Aang how convenient it was that he knew the twins. To Katara and Sokka's shock, however, Aang reveals that the story was a complete fabrication. Still hungry, he asks where the egg custard tart is, as they make their way to Appa in order to continue their journey.
When the canyon guide gets attacked by the canyon crawler, the canyon crawler picks him up using its leg, but in the next scene it is holding him with its mouth.
In the real world, the "Great Divide" most commonly refers to the Atlantic/Pacific continental divide, a mountainous ridge that separates the watersheds that drain into the Atlantic and Pacific oceans. The "Great Divide" of the World of Avatar is the exact opposite—a canyon analogous to the real-world Grand Canyon.
When the canyon guide's arms are broken by a canyon crawler, he states that he can no longer bend., which is significantly different to other earthbending styles seen in later episodes. Toph Beifong, on many occasions, uses only her legs. In addition, the earthbender in the opening sequence is seen performing the art with only his legs.
This episode was unpopular with fans due to its relatively insignificant plot and is the lowest rated episode on IMDb. This fact did not go unnoticed by the creators and in the play in the episode "The Ember Island Players", the characters chose to fly right over the canyon without stopping, highlighting the inconsequential nature of the episode's events. Avatar Extras references it by saying, "This references an episode called 'The Great Divide'", immediately followed by, "That episode was not a fan favorite."
The episode title refers not only to the geographical feature, but also to the great divide that has grown between the two tribes and the literal meaning of Wei Jin's name.