Avatar: The Last Airbender Season 2 Episode 14 : City of Walls and Secrets
Aang and the rest of the group arrive in Ba Sing Se to find Appa and inform the Earth King about the solar eclipse, but they are constantly hindered by their tour guide, Joo Dee. They soon learn that any mention of war is forbidden and enforced by the Dai Li, secret police of Ba Sing Se, and their corrupt leader, Long Feng, who appears to know something about Appa. Elsewhere, Jet repeatedly tries and fails to gather evidence that Zuko and Iroh are Firebenders. His last attempt, challenging Zuko to a sword fight, ends in his own arrest.