Aang, Katara, and Sokka stand outside the Earth Kingdom city of Omashu. Katara and Sokka believe they should disguise Aang because of their past troubles when people discovered that Aang is the Avatar. Aang assures them that the people of Omashu are very kind but when they arrive at the gates to Omashu, they see soldiers kick a man away.
The three enter the city, and Aang looks around. He then has a flashback about his young friend from 100 years ago, Bumi, who was very eccentric.
Aang persuades Katara and Sokka to go on Omashu's delivery system, which works as a system of storage containers sliding on stone chutes throughout the kingdom, much like a roller coaster. Leaping into an empty container, the three go on a wild ride through the city and inadvertently cause damage for which they are detained by soldiers.
The three are then taken to the king, who seems very old and frail and somewhat eccentric. Instead of punishing the three for the damage they caused, he treats them to a great feast, during which the king asks Aang if he wants some chicken, but Aang says he doesn't eat meat. The king then flings a piece of chicken at Aang, but Aang uses his air-bending powers to stop it.
Having thus revealed Aang as the Avatar, the king tells him that he must face some challenges and sends the three to the "dungeon", which turns out to be comfortable quarters, though there is no way to get in or out without earth-bending capabilities. Aang wakes up and discovers that Sokka and Katara are not there. Aang is taken to the king, who tells him that if he completes a series of "challenges" his friends will be set free. Aang refuses, so the king orders that Sokka and Katara each be fitted with a peculiar ring which causes a crystal to grow over their fingers and hands. The king says that it will eventually encompass their entire bodies, unless Aang accepts the challenges.
Forced to accept, Aang's first challenge is to collect a key which is hanging from a chain inside a waterfall in an underground cavern with huge stalactites and stalagmites, and no simple way to reach the key. His first two attempts fail, but Aang succeeds on the third try.
The second challenge is to find and retrieve the King's pet, "Flopsy", who is, supposedly, inside an underground arena. Aang sees a cute rabbit, and tries to catch it, but he is suddenly chased by a giant, horned, furry animal. When it appears that Aang is about to be overcome by the beast, he realizes that the monster is actually the King's over-friendly pet, and thus completes that test.
The final challenge is to face an opponent in combat. Aang is shown two fierce warriors standing in front of the King, who gives Aang the choice of whom to fight. Aang asks if he can select anyone he points to. The king says "yes", so Aang points to the frail-looking king.
The king tells Aang that he has made a mistake, because, despite appearances, he is actually the strongest earthbender in the city. He then takes off his royal robe, and straightens up, revealing a taut, but muscular, body. They fight, with Aang using his airbending powers against the king's earthbending abilities.
Aang is eventually victorious, but the king says he will release his friends, who are now nearly totally encased in the ever-growing crystal,only if Aang can answer one question: "What is my name?"
At first, Aang is mystified, but Katara tells him to think about the challenges and what he has learned from them. After some consideration, Aang finally comes to the conclusion that the king is his friend from 100 years ago, "Bumi". King Bumi then uses earthbending on Sokka's and Katara's crystal encasements, which shatter (it turns out that the crystal is "genemite", which is actually rock candy).
Aang then makes a challenge to King Bumi: The scene cuts to the two taking a wild ride on the delivery system, causing some damage, at which point the episode ends with the off-camera Cabbage Merchant shouting, "My cabbages!"