After beginning to teach Aang firebending, Zuko realizes his firebending is extremely weak, almost non-existent. Zuko tells the gang of the Sun Warriors, a firebending civilization existing centuries ago, the first people to learn firebending from dragons. Aang and Zuko head to the ruins to see if they can find anything out about firebending, but what they find is much more dangerous and surprising than they'd hoped.