Avatar Aang asks his friends to help him honour Yangchen's Festival - one of the
highest Air Nomad holidays, which hasn't been celebrated in over 100 years. But
cryptic visits from the spirit of Avatar Yangchen herself lead Aang to discover
a jointly owned Fire Nation and Earth Kingdom refinery - operating on land
sacred to the Airbenders Is this the cause of the pollution Aang finds there or
is something more mysterious happening?