The tale of Avatar Roku and Fire Lord Sozin is revealed to Aang and Zuko by different sources. Both learn about themselves and are shown the origins of the war. But will Zuko and Aang learn anything from this?

The gang meet a waterbender who lives in the Fire Nation after being captured years ago. Katara becomes her pupil to further develop her waterbending, while Aang, Sokka, and Toph discover she might be connected to a bunch of disappearances. So can this mysterious waterbender be trusted?