Avatar: The Last Airbender (season 2)
In the season's beginning, the protagonist Aang and his friends Katara and Sokka started a search to find an Earthbending teacher, which finishes when they recruit Toph. Sokka finds important information concerning the war with the Fire Nation. Aang quickly becomes single-minded in looking for his kidnapped flying bison Appa. His search leads him to Ba Sing Se, the capital of the Earth Kingdom, where he uncovers the great internal government corruption of Ba Sing Se. At the season's end, Ba Sing Se falls to the Fire Nation and Aang escapes with his friends on a recovered Appa.