Book 2 Chapter 14 "CITY OF WALLS AND SECRETS"

Aang and the rest of the group arrive in Ba Sing Se, determined to find Appa and inform the Earth King about the eclipse. They soon discover that the bureaucracy surrounding the king, enforced by the Dai Li, the "cultural authority" of Ba Sing Se, block them from making contact with him. Katara devises a plan to see the Earth King by sneaking into a party at the Royal Palace. The quartet is eventually found out and greeted by Long Feng, Grand Secretariat of Ba Sing Se and the head of the Dai Li. Long Feng reveals that the Earth King has no true political power, only serving as a figurehead and is completely unaware of the war, while Long Feng and the Dai Li control the city, ensuring Ba Sing Se remains a utopia free of war. Long Feng makes an indirect threat regarding their goal of finding Appa if they speak out, noting that they will now be watched 24/7 by Dai Li agents. Elsewhere, Jet becomes obsessed with gathering evidence that Zuko and Iroh are firebenders. His final attempt, confronting the pair at the tea shop they work in, ends in his arrest and subsequent brainwashing by the Dai Li.