Disclaimer: I do not own Avatar: the Last Airbender, it's owned by its creators Michael Dante DiMartino & Bryan Konietzko and Nickelodeon.
When Zuko returned to the Fire Nation, he arranged a meeting between his father and sister. Suki and Ty Lee were both there with him. As Azula requested Zuko left her and their father alone for a half hour, during that time she was able to gain information about Ursa. Zuko agreed to let Azula go with him to search for their mother, but he wrote to Aang that he need their help. Zuko, Azula, Aang, Sokka, and Katara traveled to Hira'a, where they met Noreen, Noriko, and Kiyi. Iroh, Suki, and Ty Lee remained in the Fire Nation. Then they traveled to Forgetful Valley and met the Wolf Spirit, and later Misu and Rafa. Then they met the Mother of all Faces, who told them what happened to Ursa, and after Aang explained about Koh, she gave Rafa his face back. Azula went after Noriko when she found out it was her mother, who had gotten a new face and no memories of Zuko or Azula. Zuko and Sokka beat her there and Zuko protected Noriko and her family from Azula. Noriko apologized for not loving Azula enough after being told the truth by Noreen,who was Ikem with a different face. Azula and Zuko fought; then Azula headed toward Forgetful Valley. The Mother of all Faces also gave Ursa her face back along with the memories. Ursa apologized to Zuko for not having loved him enough.
Ursa told her Zuko her life story. First she talked about her life in Hira'a and how she planned to marry Ikem, her boyfriend, but then Fire Lord Azulon and Prince Ozai showed up with an arrangement for marriage between Prince Ozai and Ursa. Ursa agreed to marry Prince Ozai, and on their wedding day, he told her she would have to give up her old life. She missed her old life and her family and Ikem so she wrote to her parents and Ikem. Ursa explained that Ozai treated him so badly because she had tricked him into admitting that he had been intercepting her letters and even reading them by writing a letter to Ikem pretending that Zuko was Ikem's son not Ozai's. Ozai admitted he knew the letter was false since he had her followed before they were married and led Ursa to believe he had Ikem killed; he also stated he would treat Zuko like he was Ikem's son not his own because she admitted to wishing that. Ursa also told Zuko about how she made the poison that Ozai gave Fire Lord Azulon and then he banished her, fearing that she would poison him later. She returned to Hira'a after her banishment, but her parents had died years ago. It was shortly after that she was reunited with Ikem, and she discovered he had a new face and had taken the name Noreen. He told her about the Mother of All Faces and she had her face and memories changed back.
Stay tuned...
AN: This is mostly a summary of The Search which the creators had planned to have included, but it was later scrapped. It's an important aspect of the story for both Zuko and Katara, but in this version no Katara & Aang. Katara & Aang will not be getting back together. It is important to note that Ozai and Ursa's marriage was an arranged marriage, which is the premise of this story.