As of this episode, all 4 Air Temples have been revealed.
8.4
"Great"
After a sore defeat at the Fire Nation Capital that resulted in the elders of the invasion force becoming prisoners, the gang travel to the Western Air Temple for refuge.
Meanwhile, Zuko, who had followed the group to the Western Air Temple, arrives first and descends into the temple. He remembers the last time he had been to the Western Air Temple, a week after his banishment; during which a freshly burned and bandaged Zuko proclaims that he will scour the world for the Avatar for the rest of his life and calls his Uncle Iroh lazy when he suggests rest. Ashamed of the memory, his lament is cut short as he sees Appa fly by overhead. Zuko runs off to hide and later practices his speech to convince them to accept him into their group.
While Teo, Haru, and The Duke explore, the gang discusses the next course of action. During the discussion, Sokka suggests they revert to their old plan of Aang mastering all four elements. Aang is less than thrilled at the idea, remarking that they do not know where to find a firebending teacher. Katara suggests looking for Jeong Jeong, but Aang doubts they'll ever see him again. Thinking it hopeless for the moment, he uses this as an excuse to run off and tour the temple while the rest of the group tries to think of a teacher for Aang.
When Zuko appears to the gang later at the temple, Appa licks him in a friendly manner, remembering him from Ba Sing Se. The group, however, is mistrusting. He apologizes anxiously for many of his wrong-doings, and accidentally reveals that he was the one who hired the Combustion Man to kill Aang. Zuko offers himself to them as a prisoner, but they begin to threaten him if he doesn't leave.
As Zuko laments over how terrible his attempt was, the gang ponders his motives, ultimately deciding he can't be trusted. Toph points out that Zuko was being sincere and that they need to consider him as they also desperately need a fire-bending teacher for Aang. Frustrated at the group's continued disinterest, Toph leaves.
While sleeping, Zuko hears someone coming through the bushes. It turns out to be Toph, but, unable to see in the darkness, Zuko immediately fire bends at the intruder, burning the soles of her feet as she steps back. She scurries away on her hands and knees in fear and throws Zuko far away with earthbending while he attempts to apologize and help her.
When the group wonders about Toph's whereabouts the next day, she earthbends through the wall of the cliff, falling to the ground, showing the group her burnt feet from Zuko. As Katara begins to heal Toph, they feel Zuko cannot be trusted and plan to capture him. Combustion Man appears on higher ground, ready to ambush the gang when Zuko arrives and prevents him from getting a clear shot at the gang. They find cover while Zuko tries to prevent the assassin from attacking them. The Combustion Man instead turns on Zuko and blasts him off the temple, though he manages to grab hold of a vine just in time. Aang and Katara use their bending to counter attack Combustion Man, but their lower position leaves them at a severe disadvantage from the barrage of explosions.
While under cover from the attacks, Sokka estimates the Combustion Man's position based on the angles which the explosions hit the ground. Sokka throws his boomerang, curving it around a corner, and hits the Combustion Man square on his tattoo, blocking his chi and leaving him disoriented. Combustion Man tries another attack, which backfires and causes the building he is on to explode violently. His detached metal arm is seen flying away as the debris falls into the misty canyon below.
Zuko climbs up and tries more confidently to reconcile his past meeting with the group, admitting he was wrong and that he has learned in his travels that he must earn honor by doing the right thing. He apologizes for burning Toph, stating that fire is a dangerous and wild element and that he must control his bending so that he does not hurt others accidentally. Reminded of his own fire bending experience that burned Katara, Aang decides to accept Zuko into the group as his teacher, but only if the others agree. Toph comments playfully she accepts Zuko just so she can get back at him for burning her feet, while Sokka accepts him only to help their plan of defeating the Fire Lord. Katara reluctantly agrees but only because it is what Aang wants, and Zuko enthusiastically promises not to let the group down.
Sokka leads Zuko to his own room at the temple, where he unpacks his belongings. Upon taking out a picture of Iroh, Zuko remembers his uncle's advice about destiny. Immediately afterwards, Katara confronts Zuko and warns him that he may have the others fooled, but they both know this isn't the first time he has struggled to do the right thing. She makes a very clear threat to his life: should he give her any reason to think he would hurt Aang again, she'll personally make sure his destiny ends permanently. She leaves the room while a silent, stunned and reverent Zuko ponders her words.