The Legend of Korra: 3x4

Chapter Four: In Harm's Way

Lord Zuko, Tonraq, Desna, and Eska try to prevent Zaheer from freeing the last prisoner, P’Li, while Korra discovers that the Earth Queen is forcing all the airbenders in Ba Sing Se to join her army. Team Avatar thus devises a plan to free them from the monarch’s captivity.