In another age, power is balanced among four great nations: Water, Earth, Fire, and Air. Leaders of each nation are able to bend their native element. Only one bender, the Avatar, whose spirit is reincarnated through the years, can master all four elements and maintain the world order. After disappearing for a hundred years, the Avatar returned as Aang, a twelve-year-old Airbender. It is up to him to save the world from being dominated by the Fire Nation.