The Library Sinks and Appa is Kidnapped

In this chapter, the characters are faced with an impossible choice: save their friends trapped in a sinking library or save their new friend, Appa, who is being dragged away by sandbenders. Meanwhile, Katara and Momo are being chased by Wan Shi Tong, the spirit of the library, until they face off on a bridge. Sokka manages to knock out the spirit with a heavy book, and Professor Z decides to stay behind in the library. The group climbs to safety, while Toph lets go of the tower and is thrown back, leaving a crater where the tower once stood.