Here is the plot for the 4th book of Avatar: The Last Airbender
Book 4: Reformation.
They restart it as Firelord Zukko trying to rebuild all of the 4 nations. Everything is going fine, until Azula escapes from prison and takes previous firelord Ozai with her. All hell breaks lose and Aang and the gang get back together to solve the problems. Azula finds a few loyal firebenders and others, June amongst them, and plans to get back what was rightfully hers. But with everything that is going on, everyone seems to be having trust issues. Zukko is having problems trusting Mae, thinking she had something to do with Azula escaping. While Katara is worried that Aang has his eyes on some other girl, Toph. Zukko and Katara go off on their own, feeling like they don't fit in with the group anymore, and their relationship intensifies. Meanwhile, Uncle Iroh is just walking around minding himself, finding new leaves for his tea shop, and he runs into Azula, she takes him prisoner and threatens him to help her sneak into the palace. Iroh won't tell her anything so she then ends him, for good. The Nations hear about it and they freak out more than normal. It's time for Team Avatar to restore peace in the world, for good. And also for Zukko to really find out about his mom and find her once and for all.