The episode opens at night, with a crowd (including Aang, Momo, Katara and an apparently bored Sokka) surrounding a fire pit listening to a storyteller’s account of his great-grandfather’s encounter with secret air walking people who laugh at gravity. After his tale is done and the story teller goes around with his hat for contributions, Katara asks Aang if the airbender stories are accurate and Aang replies that he laughs at gravity all the time. When the storyteller comes to Sokka for a contribution; Sokka shows that he has no money and sheepishly says sorry. Aang thanks the storyteller and tells him how great it is to hear airbender stories and that it must have been over 100 years when his great-grandfather saw the airbenders. The storyteller sharply asks Aang what he is talking about as his great-grandpa saw the airwalkers just the previous week.
Excited at the possibility of there being airbenders at the Northern Air Temple, the gang heads there. As the temple comes into view there are gliders circling it and Aang’s excitement shows on his face; only to fall a few seconds later as Aang realizes they are not airbenders, but non-airbenders using gliders. Suddenly, one of the gliders with a chair attached swoops by them. Aang sees this as a challenge and leaps off Appa with his glider in order to show them what a real airbender can do. Appa takes the Katara, Sokka and Momo to the temple to watch as the glider (Teo) and Aang face off in a sort of air duel. Aang shows some of his airbending moves and then Teo does a skywriting caricature of Aang with an annoyed look on his face – which happens to mirror Aang’s facial expression upon viewing it. Both Aang and Teo head in to land at the temple. Other residents remove the glider from Teo’s chair to reveal he is in a wheelchair. As Teo wheels himself over to Aang, Sokka and Katara, he exclaims “Hey, you’re a real airbender!” which seems to lighten the mood between the two competitors.
Teo takes them into the temple where pipes, pulleys chutes and chimneys have been installed throughout the temple. While Sokka is amazed, Aang is shocked by what he sees as a violation of his cultural history. Teo takes then to an outside coliseum type area that appears to have been untouched, but just as Aang expresses his happiness to have found this, a wrecking ball breaks through the wall destroying a huge statue of an airbending monk. Aang angrily yells at the leader about how this destruction of a sacred place in order to install a bathhouse stinks. He then forces the wrecking ball machine off the mountain with a single air blast. Teo tells the leader (his father) that Aang is the Avatar and used to come there 100 years ago. Teo’s dad explains how they came to live there (not by choice, but by necessity) several years ago after a flood wiped out their village and took Teo’s mother’s life. He, an inventor, states they are just improving on what was here, but Aang disagrees saying that nature knows when to stop. Teo’s father agrees that sometimes progress can go too far. Sokka is impressed with Teo’s father’s inventions and follows him to see more.
Teo takes Aang and Katara to see the sanctuary door, which looks similar to the Southern Air Temple’s, and tells Aang that at least there is something is just as it was when Aang was there last. Although he knows Teo would like to see inside, Aang refuses to open the door - not wanting to taint what is left of the temple and Teo understands.
The inventor takes Sokka down a staircase as they hold lanterns filled with fireflies – which puzzles Sokka. As they reach a door, the inventor checks the fabric seal around the door and tells Sokka to hold his breath and look through a small sliding door opening. The inventor explains that beyond the door is natural gas – which is why they are using a non-flammable source of light. The inventor is currently working to resolve the problem of detecting gas leaks in order to prevent a future explosion.
Outside, Katara prepares to use a glider for the first time as Teo instructs her. Katara is afraid she doesn’t have it in her to go through with it, but Teo tells her everyone has “it” and Aang give “it” a name - spirit. Katara takes the plunge and after an initial nervous few seconds, allows her spirit to guide her. Teo and Aang follow her and Aang advises her to keep her mouth closed so she doesn’t swallow a bug. Aang and Teo land and Aang tells Teo he has decided to show Teo the sanctuary despite his earlier reservations about it.
Back in the inventor’s workroom, Sokka knocks over an old experiment and a rotten egg. They frantically look for the rotten egg.
Aang then uses his airbending to open the sanctuary locks.
The inventor and Sokka realize the answer to the natural gas problem is to put rotten eggs in the room with the natural gas so that when there is a leak they will smell rotten eggs. As they congratulate each other, a bell goes off and the inventor says he has to go. Sokka follows.
The doors of the sanctuary open to reveal to Teo, Aang and Katara an arsenal of weapons including a balloon with the fire nation emblem. The inventor arrives with Sokka. The inventor explains that a year after the moved there, the Fire Nation threatened the residents - forcing the inventor to provide weapons for the Fire Nation in order to survive.
Back in his workroom, the inventor lights a model balloon and Aang and Teo follow him there. Aang asks when the Fire Nation is coming and the inventor says very soon. Teo tells his father he can not be proud of him when his inventions are used for murder. Just then, the Fire Nation arrives and Aang and Teo hide in the room. As the inventor is about to lead the officer to the weapons, Aang slams the door shut and stops them from leaving the room; telling the officer he will be leaving empty handed. The Fire Nation officer tells Aang that the destruction of the Temple will be Aang’s fault and then leaves.
Aang explains that they can defeat the Fire Nation as they control the skies and Teo’s dad says he wants to help. Back in the inventor’s workroom, Sokka explains how he came up with a solution to the balloon issue – a lid. Even Katara is impressed. They ready themselves for the Fire Nation attack and head out into the skies – hitting them with their various bombs. Despite their best efforts, the Fire Nation advances. The tank-like machines appear unstoppable even after Aang blows them away with air blasts. The center part of the machines is counter balanced to self-level and then moves forward again. Realizing the counter balance is done with water, Katara uses waterbending to stop a few of the machines. The gliders are out of bombs and suddenly the war balloon with Sokka and the inventor shows up. The Fire Nation soldiers do not attack the balloon because of the flame emblem. After deploying all the weapons they have, Sokka and the inventor notice a rotten egg smell. Realizing the opening in the ground below them is where natural gas is escaping, Sokka and the inventor use the balloon’s engine to ignite a huge explosion - blowing the Fire Nation off the mountain as well as destroying the access to the mountain. As the balloon goes down, Aang heads down on his glider and Sokka throws his boomerang attached to a rope toward Aang who pulls the two of them back up to the temple.
Aang tells Teo and his father he is glad they are living there. Teo says that means a lot coming from him. Sokka states as long as they have the air the Fire Nation can be kept away; however, the introspective inventor realizes something they don’t. Just then, in the forest, the Fire Nation can be seen recovering the lost balloon and the officer ominously says “This defeat is the gateway to many victories.” The episode ends as the Fire Nation is re-inflating the balloon, confirming to the viewer the inventor’s worries.
