Avatar Aang asks his friends to help him honor Yangchen's Festival--one of the highest Air Nomad holidays, which hasn't been celebrated in over one hundred 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 a more mysterious menace afoot? *...