The world is divided into four kingdoms, each represented by the element they harness, and peace has lasted throughout the realms of Water, Air, Earth, and Fire under the supervision of the Avatar, a link to the spirit world and the only being capable of mastering the use of all four elements. When young Avatar Aang disappears, the Fire Nation launches an attack to eradicate all members of the Air Nomads to prevent interference in their future plans for world domination. 100 years pass and current Fire Lord Ozai continues to conquer and imprison anyone with elemental "bending" abilities in the Earth and Water Kingdoms, while siblings Katara and Sokka from a Southern Water Tribe find a mysterious boy trapped beneath the ice outside their village. Upon rescuing him, he reveals himself to be Aang, Avatar and last of the Air Nomads. Swearing to protect the Avatar, Katara and Sokka journey with him to the Northern Water Kingdom in his quest to master "Waterbending" and eventually fulfill his destiny of once again restoring peace to the world. But as they inch nearer to their goal, the group must evade Prince Zuko, the exiled son of Lord Ozai, Commander Zhao, the Fire Nation's military leader, and the tyrannical onslaught of the evil Fire Lord himself.
The film was originally titled "Avatar: the Last Airbender", after the TV show it was based on. However, James Cameron and 20th Century Fox had already registered the film title "Avatar", so the word was dropped from the title to avoid confusion.
[from trailer] He will need you... and we all need him.
Revealing mistakes: During the first conversation between Fire Lord Ozai and General Zhao we can see that Ozai's eyes move from left to right while he looks in the direction of Zhao's chest, thus revealing the use of a prompter.