Zuko prepares to teach Aang firebending, but discovers that his own abilities have significantly diminished. He and Aang travel to the temples of the extinct Sun Warriors to learn about the ancient origin of firebending. Zuko reveals to Aang that his great grandfather, Sozin, caused the extinction of the dragons, the original firebenders. After discovering the Sun Warrior culture still exists, Zuko and Aang are sent to see the firebending masters, later revealed to be the two last surviving dragons in the world: Ran and Shaw. After the dragons teach them the true nature of fire, Zuko's powers are restored and Aang no longer fears nor hates firebending.
Zuko commences Aang's firebendingtraining at the Western Air Temple and tells Aang to show him how much fire he can produce. Seeing as it is not very much, Aang thinks perhaps a demonstration from Zuko would help. However, Zuko finds that his own firebending is very weak; he tries to firebend at lower altitudes, hoping that it is the height hindering him, but to no avail.
Later that night, Zuko apologizes to everyone, saying he has lost his firebending. Out of spite, Katara laughs and coldly jokes how convenient it would have been for the group if Zuko's firebending had failed him months before. Aang hypothesizes that Zuko must not have enough rage to create fire like he used to in the past. Sokka, stating that all they would have to do is make Zuko angry, starts poking him wildly with his sword sheath. However, Zuko says that he no longer wants to rely on anger and hatred, so Toph encourages him to learn from the original source of firebending, like how she learned earthbending from the badgermoles, who were the original earthbenders. Zuko says that the dragons were the original firebenders, but that they have been extinct for some time. Flabbergated, Aang comments that when he was a kid there were many dragons and AvatarRoku had a dragon, but Zuko does not find it very helpful. Knowing that either he needs to find another way to firebend or the Avatar needs to find a new teacher, Zuko tells Aang about an ancient civilization that died out thousands of years earlier called the Sun Warriors, hoping the ruins of the culture could provide an alternate but equally viable source.
Zuko and Aang fly to the Sun Warrior ruins on Appa, they land and start exploring the ruins. Aang nearly falls into a trap, which Zuko is surprised to see still works even after centuries of being built. He bypasses the trap by running across the adjoining wall. Aang is hesitant to continue, but Zuko edges him on and they find a massive stone carving depicting dragons and a Sun Warrior.
In the mural, two of the dragons are breathing fire onto the Sun Warrior. Aang is surprised because he got the impression that the dragons were friends with the Sun Warriors, while Zuko remarks that they had a funny way of showing it. Aang asks Zuko what happened to the dragons, and Zuko reveals that the dragons became extinct because Fire LordSozin started the tradition of hunting them for glory and the title of 'Dragon'. He tells Aang that the person who killed the last living dragon was his uncle, Iroh.
While exploring the ruins, Aang and Zuko come across a locked door with a sunstone on top. Zuko sees a celestial calendar is used to open the door specifically on the summer solstice and uses his sword to reflect sunlight onto the jewel, causing it to open. Aang compliments his intelligence, telling him he "doesn't care what anyone else thinks". Inside they find various statues which depict a firebending form called the Dancing Dragon.
Aang imitates the first statue and discovers there are tile switches linked to the dance positions. He persuades Zuko to perform the dance with him and as they do, they activate an ancient key mechanism. Upon completion of the Dancing Dragon, a pedestal with a huge gold, egg-shaped gem rises in the middle of the room. Zuko picks it up despite Aang's warnings, inadvertently triggering a trap. The chamber doors close, and a viscous slime fills the room. Zuko and Aang find themselves trapped by the liquid in a barred skylight where they have plenty of air but no way to get free. They are subsequently captured by the still-flourishing Sun Warrior tribe, which accuses them of attempting to steal Sun Warrior treasures.
After explaining that Aang is the Avatar and they desire to learn the true form of firebending, Zuko and Aang are put through a ritual where they have to carry a portion of the first fire, given to man by the dragons, up a mountain and present it to the true "firebending masters", Ran and Shaw. At first, Aang is scared to try to hold the flame, but the Sun Warrior chief comforts him by saying that fire is not just destructive, but it is life.
They reach the lair of the masters and are sent to the top of a stairway, where they see two caves at the top. Aang and Zuko present their fires and each face one of the two caves. Aang, however, loses his portion of the fire due to being distracted and scared; he tries to take a piece of Zuko's fire, but accidentally knocks his hands down, extinguishing his flame as well. At that moment, two dragons emerge from the two caves, to Zuko and Aang's great shock, and start flying in circles around them. Zuko and Aang earn the respect of the dragons by performing the firebending technique that they learned from the statues, dancing with the dragons in the process. The dragons breathe beautiful, multicolored flames around them, revealing the true and harmonious way of firebending.
When the dragons return to their caves, Zuko understands the reason he could not firebend was because he had lost his "inner fire". He used to draw his fire from rage, anger, and his burning desire to capture Aang, but after he joined the group, he could no longer draw from this source. However, after watching the dragons, he learns that he can draw from the true source, his desire to help bring balance to the world. He describes this new found feeling as "the sun but inside of you".
Aang realizes that fire is not destruction, but energy and life, and is able to firebend as well. The chief explains that Iroh was the last outsider to visit the masters and deemed worthy to learn the secret. He lied to keep the dragons alive so they could continue on. The chief explains he has no choice, but to imprison the both of them forever to keep their existence a secret, which astonishes them both. He soon reveals that he is joking, but is very serious that they do not tell anyone.
Back at the Western Air Temple, Zuko and Aang show everyone the firebending moves they learned. Sokka pokes fun at them by saying that they would just "tap-dance" their way to victory over the Fire Lord. Zuko tries to explain how serious and ancient the technique is, but they cannot look past the name of the form, the "Dancing Dragon", so they do not take it too seriously.
This episode shows Toph learning earthbending from badgermoles. She had previously stated she learned the art from them in "Sokka's Master".
Katara continues to be cold toward Zuko after he was finally accepted to the group in the previous episode. She remarks at the irony of him losing his firebending.
The song chanted by the Sun Warriors to call forth the Masters is the same as the Avatar series ending credits song.
The close-up of Aang shown as his first burst of fire is disappearing mirrors the close-up from "The Deserter" when he makes a ring of fire that results in Katara's being burned. That episode taught him the dark side of firebending and caused him to steer away from ever using it again; this one teaches him the true art, thus breaking that mental block.
Sokka mocks Zuko by suggesting he should jump into a volcano. In the following episode, Sokka and Zuko both literally jump into a volcano.
Aang calls Zuko "Sifu (Master) Hotman", a reference to his knowledge of what was common slang in the Fire Nation a hundred years prior.
From this episode on, Zuko does not grunt in anger every time he firebends, which was something he did frequently in seasons one and two and part of season three.
When Sokka approaches Zuko and Aang and asks if he can watch "you two jerks do your jerkbending", his right hand holding his apple goes from being bare, to gloved, to bare again. His left hand is also seen going from gloved to bare.
When Sokka attempts to make Zuko angry by poking him, Appa is seen eating in the background, but when Zuko says he does not want to rely on hate and anger anymore, Appa is missing.
When Zuko tries to "speed up time" by manipulating the sun stone-activated chamber, he takes out one of his dual swords. A few frames later, however, he has both out.
After Zuko is catapulted to the ceiling, the egg he was holding is seen dangling next to him because of the viscous slime, but when Aang tries to airbend at Zuko to free him from the glue, it is gone.
When the Sun Warriors show Aang and Zuko the first fire that was given to man by the dragons, they are seen sitting in three rows, but in a later frame there is only one row.
When the Sun Warrior instructs Aang and Zuko with, "Those who wish to meet the masters Ran and Shaw will now present their fire," Aang and Zuko are already in a bowing position, offering their fire. When it cuts back to a close-up of them, they are merely standing and staring at the procession of Sun Warriors below them before assuming a bowing position.
The music the Sun Warriors play, as Zuko and Aang walk up the stairs, is noticeably off beat. The motions made by the drummers do not match the "chuu-chaa-chuu-chaa-chuu-chaa" noise.
When Zuko and Aang are being surrounded by the dragons' fire, for a split second, Zuko's scar can be seen on his right eye instead of his left.
Iroh stated to Zuko in "Bitter Work" that firebending is fueled by rage and emotion, despite having known the true motivation behind the bending art.
When Zuko is about to raise the golden artifact, Aang states that he is "very suspicious of giant glowing gems sitting on pedestals", most likely alluding to a similar situation concerning the booby-trapped golden idol from Raiders of the Lost Ark.
Ran and Shaw resemble the red and blue dragons from Zuko's fever-induced dream in Ba Sing Se.
The Sun Warrior's architecture resembles that of Indian Buddhist Stupas and Tibetan monasteries.
The bowing gesture demonstrated by the Sun Warriors during Ran and Shaw's judgement is identical to the bowing gesture demonstrated by Kwan's students in "The Headband".
The final move of the Dancing Dragon is reminiscent of the "Fusion" move in Dragon Ball Z.
The entire Dancing Dragon form bears a striking resemblance to the real life Long Ying Mo Kui, the traditional Southern Dragon kung-fu style.
While climbing the mountain, Zuko tells Aang he is a talented kid and that he can control his fire in order to ease his anxiety and give him confidence. This is another example of how well Aang responds to positive reinforcement.