Avatar: The Last Airbender -- Smoke and shadow

When the Fire Nation begins to believe that the country will perish if Zuko stays in power, Avatar Aang and his friends must protect the ruler.

"Children are disappearing in the Fire Nation capitol! Avatar Aang and his friends are doing everything in their power to save them--but will it be enough?! What's worse, when Azula--the mad sister of Fire Lord Zuko--appears on the scene, Zuko locks down the capitol to catch her, igniting fear and riots in the streets! Will Zuko follow in his evil father's footsteps in order to save those he holds dear?!"--Amazon.com.