The day her brother returned Azula was still in her room. She watched through the barred, curtain-less window as his carriage pulled up to the front of the house. She saw him get out, his head low and shoulders slumped. Aang and Katara were there to greet him. Azula watched him put his hands on their shoulders, watched Katara's hand jump to cover her gaping mouth. He knew the truth. He had broken the promise. She had seen this betrayal coming from miles away, but it still stung like a knife. She watched Zuko stand up straighter and stride through the door of the palace. He was coming to confront her.
Zuko would have only one choice, now that he knew exactly what Azula was. The deals they had made before would be voided. It was over now.
Azula had written her father dozens of times since returning from her exile. He had always been a symbol of strength, competence and control to her. As long as she stayed on his good side, as challenging as that could be, the world would be hers and no harm would come to her. Until one day she would be old enough to command that level of strength and competence and control herself. Perhaps that's why she had been compelled to write to him. But at the end of the day all that strength had not done him any good. The world had changed out from under his feet, and left him an old man locked in a dark cell. He could not help her, even on the slim chance he would want to.
Ignoring the pain in her lower back, she sat and wrote a letter to the one person who could, to one person she had been too frightened to write before. Her hands shook as she inked out the header. She had all her life wondered what it was like to fully be in control, but never had asked what it was like to be subject of it. She thought it would be hard to write, but after all her years of priding herself on her wit and her ability to lie, telling the truth in it's entirety was not difficult. Once she started writing the words flowed easily.
She fanned the ink with her gloved hand, sealed it up with a little wax, and rose to her feet to take it to the falconry. She would send it on a hawk herself. Her maid-servant could no longer be trusted, though even the hawks were often intercepted, a risk she had to take.
After completing this, she decided not to put off the inevitable. She went to confront Zuko. No body betrayed her trust without consequences, even if she should have expected it all along.
She made her way across the great throne room to the little office attached to the side, what had once been Father's office, what should have been hers.
She didn't knock.
He looked up from doing nothing and scowled.
"You went to Ba Sing Se," she said. "When you told me you wouldn't do any more digging into my past."
"I realize why now," he said. "You dare ask me to respect your privacy after what you did... This changes everything, Azula. I wish with all my heart I could unlearn what I discovered but I can't."
"I didn't come here to speak to you about that. I came to speak to you about the fact you made me a promise which you had no intention of keeping. I should have known not to trust you."
"Trust," Zuko began to turn crimson. He suppressed a laugh. "You talk to me about trust while you keep a secret like this. You don't think I should have know the truth before I let you live in my house, walking around my halls?"
"You didn't let me in, Zuko, I'm your prisoner!" She said. She stepped forward, bringing her face within a foot of his. Her hands were beginning to smoke from underneath her silk gloves.
"I could throw you in a real prison if you wanted," Zuko said.
"I'd prefer that than this charade of yours about how much you care about me and my health. I dare you to."
"It would be nothing less than what you deserve," he said. "You know, I really thought you were protecting someone when you asked me not to search through your past. I really wondered who it was. Scenario after scenario crossed my mind who this lover of yours was. Perhaps he was cruel to you. Perhaps he had been your partner in crime and you wanted to spare him the punishment of the law. Perhaps this child had been conceived through some twisted impropriety. None of them made made any sense to me, though I could not think of what else it could be. In hindsight it should have been obvious exactly who you were trying to protect." He stood up. His face darkened. "I came to my office hoping to cool down before I confronted you, but I don't have a choice now. I know exactly why you didn't want me searching for the father of your child. It was because you knew I wouldn't find him."
Azula scoffed. "Then you know nothing?"
"I know that his name was Hiro, born 20 years ago in the Fire Nation Colony of Yu Dao to middle class parents who were killed during the uprising. He was nothing more than a day laborer. And the reason you knew I would not find him is because he is dead. You killed him with your own hands."