Sokka and his sister Kya - later renamed Katara, must travel the world to find masters for Aang, who is the Avatar. However, they must evade a critical foe, Prince Zuko of the Fire Nation, who wants to capture Aang.
The gang arrives at Kyoshi Island and are captured by some Kyoshi warriors. When Aang reveals that he is the avatar, news quickly spreads out and suddenly reaches to Prince Zuko who then goes to Kyoshi Island to capture him.
In a nearby Earth Village, the gang meets a teenage earthbender named Haru. This village lives in fear of the Fire Nation, for soldiers there capture any earthbenders they can find.
To contact the spirit of the previous Avatar, Aang must reach a temple in the Fire Nation before the sun sets on the following day. There he will learn what he must do to restore balance to the world. Zuko must defy his banishment to follow Aang.
Aang relives the events after finding out that he is the Avatar 100 years ago and tells them to Katara, while Iroh tells the story of Zuko's scar and banishment to the crew.
Sokka and Katara meet a friend of their father who offers to take them to join the Water Tribe's navy. Aang fears his friends will choose seeing their father again over staying with him.
While Katara herself becomes a great waterbending master, Commander Zhao plans a siege on the Northern Water Tribe. Meanwhile, Sokka's on a mission to stop this siege while Aang tries to buy them some time.