The show follows Aang (Zach Tyler Eisen), the last airbender and the “Avatar”, on his journey to bring balance to a war-torn world by mastering all four elements: air, water, earth, and fire.

On his quest, he is joined by companions Katara (Mae Whitman) and Sokka (Jack DeSena) and hunted down by Fire Nation prince Zuko (Dante Basco).

The episodes mark Isaacs' final appearance in the series as Zhao, as well as the introduction of Koh the Face Stealer (Erik Todd Dellums) and Zuko's sister Princess Azula (non-speaking role).

While Katara is making heavy progress in her training with Master Pakku, Sokka takes Yue on a date aboard Appa where they notice a fleet of Fire Navy ships approaching the Northern Water Tribe.

Iroh learns from Zhao that he found an underground secret library[b] that revealed to him the identities of the Moon and Ocean spirit, from which the waterbenders derive their power.

Flying on Appa, Sokka, Katara and Yue find Zuko just as Aang exits the spirit world and enters back into his body.

[c] Aang enters the Avatar State and merges with the Ocean spirit to create a monster that wreaks havoc on the Fire Nation forces, and drives away the fleet of ships attacking the Water Tribe.

Iroh and Zuko escape on a tiny boat that drifts into the unknown, while Aang prepares to set off on more adventures to stop the Fire Nation with Katara appointed as his new waterbending master.

Main cast members Zach Tyler Eisen, Mae Whitman, Jack DeSena, Dante Basco and Dee Bradley Baker appear as the voices of Aang, Katara, Sokka, Zuko, and Appa respectively.

Appearing in both parts are guest stars: Mako as Zuko's uncle Iroh, Jason Isaacs as Admiral Zhao, Jon Polito as Northern Water Tribe Chief Arnook, Victor Brandt as waterbending master Pakku, Johanna Braddy as Arnook's daughter Princess Yue, and Ben Diskin as Hahn.

Guest starring in part 2 only are Erik Todd Dellums as Koh the Face Stealer, James Garrett as Aang's previous incarnation Avatar Roku, and Mark Hamill as Fire Lord Ozai.

Club praised the two-part episode for its tension building and fairy tale feeling, stating "As in so many other stories, Book 1 all comes down to a giant holy fish monster and a girl who sacrifices her life to be the moon.