The info they find leads them to island not on the map.
While in the North Pole, Aang and Katarra hear that the water bender, Hiryu has gone missing which they go to investigate. They manage to fend off the ship but Katara is captured during said battle.
Aang goes hot in pursuit and chases Lian and her machine to a fortress.
After rescuing his friends, they find Zuko who has been kidnapped by a machine..
After rescuing them, Zuko attacks the group, at the end of the fight he is knocked over a waterfall.
The 4 enter the fortress where they find Lian, where she finished a machine which is manned by the missing waterbender Hiryu, Haru’s friend Yuan, and a fire bender.