This article is about the episode. For the location, see Foggy Swamp.
"In the swamp, we see visions of people we've lost, people we've loved, folks we think are gone. But the swamp tells us they're not. We're still connected to them. Time is an illusion and so is death."
— Huu explaining Team Avatar's illusions.
While flying, Aang and friends are attracted to a mysterious swamp and get separated from one another. They begin to see unique illusions in the swamp: Sokka sees Princess Yue, Katara sees her dead mother and Aang sees a mysterious giggling girl. They are reunited and attacked by a swamp monster, who turns out to be a wise man from a tribe of swamp waterbenders. He explains the nature of the swamp and their visions, including that the girl is someone Aang will meet. Meanwhile, Zuko and Iroh are forced to live life as commoners. Disguised, Zuko resorts to using his Blue Spirit guise to help himself.
The episode opens with Zuko and Iroh begging for money in a village street. Zuko refuses to grovel, trying to keep what dignity he has left, while Iroh has more willingly accepted their new lot in life. A swordsman approaches Iroh and has him sing for a gold coin. As Iroh sings, the swordsman swings his blades at Iroh's feet to have him "dance". As the swordsman leaves, Zuko is angered and humiliated by his uncle's degradation.
Meanwhile, Aang, Katara, and Sokka are seeking an earthbending teacher for Aang as they fly over a swamp. Aang feels the swamp is calling to him, but, due to the reluctance of his friends, agrees to leave. Suddenly, a tornado appears, swallowing everyone into the swamp. Aang uses airbending to make a sphere of air as a shield around Appa, but the tornado overwhelms and dispels the sphere, pulling everyone into the windstorm. This separates humans and animals into two separate groups.
The human group begins looking for Momo and Appa. Aang and Katara are wary of the environment, sensing something ominous about it. Sokka uses his machete to hack through the swamp vegetation, clearing a path. He becomes annoyed at his sister and friend's warnings, stating there is nothing out of the ordinary about the place.
Aang, Katara, and Sokka make camp for the night. While they are asleep, a swamp monster attacks them, which ends in a further separation of the group. Alone in the swamp, each person experiences a vision of another person. Katara sees her mother, and momentarily believes she has returned. However, after joyfully running over to meet her, her vision is revealed to be an ordinary stump to which Katara gasps in disbelief and breaks down into tears. Sokka envisions Yue in spirit form, who says hauntingly to him, "You didn't protect me." Sokka refuses to believe what he witnesses, clinging to the belief that there's a logical explanation. Aang spots a young laughing girl and a flying boar in the swamp, the girl of whom he does not recognize. He calls out to her, but she runs away. Aang begins to chase after her.
The two animals are confronted by the swamp-dwelling hunters Tho, Due, and their brethren in canoes. Tho attempts to coax the animals toward him, but is unaware they understand his human speech, and accidentally mentions that they will become food once captured. Appa and Momo flee as a result. Due shouts angrily at Tho for his ignorance; Tho defends himself by asking how he was to know about the animals' intelligence. To catch up with Appa and Momo, Tho begins bending the water around his canoe, causing it to speed forward rapidly.
Aang is still seen chasing the girl. Eventually, when he thinks he corners her, the vision of the stranger disappears with Katara in her place. Sokka drops in, literally, and they all confess their encounters. Aang and Katara wonder about the mysterious workings of the swamp, but Sokka continues to insist nothing is out of the ordinary until a giant swamp monster attacks them. It manages to grab Sokka and swing and slam him against the river. Aang frees Sokka by sending an air blade toward it, but the monster then attacks him. The swamp monster then grabs Sokka again and tries to surf away, but its arm is damaged by Katara's waterbending. It still holds onto Sokka, even after Katara forcibly pushes it away with a large wave. Katara is then pushed back along with Aang, who had come back. From twisting and tangling its body with a tornado to Katara creating a big hole with a water drill or slinging an array of water blades, it does not seem affected, instead replacing its armor of vines. Yet with each cut, they see a man inside the monster, and one more water blade from Katara through the "head" forces the man to give up.
They demand to know who the waterbender is, but the mysterious figure wishes, in turn, to know why the three are in the swamp. Sokka reveals that Aang is the Avatar and that "stuff like this happens to [them] a lot." Understanding that the swamp chose them, the bender reveals his name: Huu. He reveals the reason he attacked them was that he was protecting the swamp which Sokka was harming. He takes the three friends to the roots of an enormous tree, the heart of the swamp. Huu's story reveals that he achieved enlightenment under this tree, and saw how the entire swamp is the roots of the single tree spreading for miles. He says that everything is connected, how time and death are only illusions, and that the swamp manifests visions of deceased loved ones to show how they are still present spiritually. Aang asks about the girl he saw, stating it was no one he knew, but eventually figures out that the girl is someone he will meet in the near future. Aang touches the tree, connecting to the swamp. Far away, he sees Appa and Momo being chased. Aang, Katara, and Sokka then rush to the animals' aid. When they finally arrive, Aang and Katara use waterbending against Due and Tho, but the swamp-dwellers use waterbending themselves. Upon this discovery, the fighting stops. Tho and Due unite with Huu, who had followed the gang, showing the waterbenders know each other.
The scene switches to Aang, Katara, and Sokka sitting around a fire in the swamp-dwellers' camp. Aang and Katara continue to wonder about the swamp, but Sokka is steadfast that there is nothing out of the ordinary. The next moment shows a bird perched on a root; a vine rises from the ground then lashes out at the bird making it take off.
The last scene shows the swordsman, who mistreated Iroh and Zuko, in a dark alleyway. He senses someone there and pulls out his blades, demanding that the person show their self. Two hands grab his wrist, making him release the blades, and he is thrown into a stack of crates. The mysterious attacker is revealed to be the Blue Spirit.
Back in the "The Blue Spirit", Momo found an assortment of trinkets for the ill Katara and Sokka, including an old crown for Katara. That crown makes a comeback in this episode when Momo throws it at the waterbenders chasing them, while he and Appa tried to escape.
When Sokka yelled out, "Why do things keep attaching to me?" while pulling off the elbow leech stuck to his arm, he was referring to the purple pentapuses that stuck to his face in the previous episode, "Return to Omashu".
When Sokka asks Huu about the tornado, Huu responds by saying, "I can't do anything like that; I just bend the water in the plants." This introduces the idea of plantbending and foreshadows the concept of bloodbending, seen later in "The Puppetmaster".
This is the first time we see Katara and Sokka's mother, albeit from behind and as a vision. She makes her first real appearance in "The Southern Raiders", though only as a flashback.
This is Toph's first appearance on the show, namely, as an eerie vision seen only by Aang. She is formally introduced in "The Blind Bandit".
The mask cart that passes Iroh and Zuko in the opening scene bears the same blue oni mask that Zuko uses for his Blue Spirit alter ego. When the mask is seen, we can hear the Blue Spirit's leitmotiv. This foreshadows the ending of the episode, in which Zuko has reassumed its identity.
Zuko gets himself new broadswords in this episode from the swordsman, who forced Iroh to dance for a gold piece.
Huu gaining enlightenment under the Banyan tree is similar to the Buddha's enlightenment.
In "The Swamp" with "Avatar Extras" bonus commentary, the plantbenders' pet alligator "Slim" was revealed to be named after one of the creator's two dogs.
The song Iroh sings at the beginning sounds strikingly similar to the song "It's a Long Way to Tipperary".
The swamp seems, mostly when shown from above, similar to the Toxic Jungle from Hayao Miyazaki's Nausicaä of the Valley of the Wind.