Book 1 Chapter 20: The Siege of the North (Part 2) Zhao's invasion breaks through the outer wall of the Northern Water Tribe's defenses, and he reveals a sinister plan to destroy the city.
Heeere's the season finale! Epic battles, a journey into the Spirit World, a face-stealing monster, sinister plots....too much awesome to summarize in one paragraph! And so ends the Book of Water. Next is the second season, which is Earth! Go join avatar_episodes if you want more!