A village comes to Aang seeking help; a spirit called Hei Bai comes every sunset, destroying their town and kidnapping their villagers. As the Avatar, its Aang's duty to stop the spirit, despite the boy having no idea how. Sokka attempts to help Aang, but only manages to get taken himself; Aang returns, having failed to stop the spirit or save any of the lost people...only to discover that he has no physical form or voice. He has become trapped in the Spirit World.