S1E17 · Book One: Water - Chapter Seventeen: The Northern Air Temple

Complete story — includes the ending

The gang hears a rumor that people who travel in the air reside at the Northern Air Temple, making Aang think there were some survivors of Sozin's genocide. He is disappointed to learn that the "flying" people are not true airbenders, but just people who have learned how to use gliders on the strong air currents around the temple. Aang is further saddened that the current residents have remodeled the temple extensively, often knocking through walls and ornate Air Nomad architecture to accommodate pipes which propel their rudimentary experiments with steam pressure. Teo, a young paraplegic, inspires Aang to open the one remaining area of the temple left untouched, the Air Temple sanctuary. Aang is shocked to see the "pristine" room is in fact stocked with dozens of inventions with Fire Nation insignias on them. Teo's father, a skilled mechanist, confesses to aiding the Fire Nation by building weapons in exchange for the guaranteed safety of his son and his people. When the Fire Nation comes to collect their latest invention, Aang tells them to leave. The Fire Nation launches an attack against the temple, but Aang and the villagers manage to successfully defend their ground. The Fire Nation does manage to recover the mechanist's newest invention, a war balloon.