It wasn't a secret, really. Just something he'd never told her.
It was a warm night, and Zuko was lying there, one arm around Mai, who was sound asleep, curled at his side with one of her delicate hands on his bare chest. He couldn't sleep, so he stared at the ceiling, his ming churning over two events.
That very evening, standing at the end of this bed, Zuko had kissed his wife and she'd placed her hands on his face. He'd pulled back to look at her, the way he always did. She was beautiful, how could he not? And Mai had looked back at him and her hand had slid up his face, feeling his skin, one hand getting close to his left eye –
"Mai." It was not angry or cold, just a reminder. He'd never said as much, but she was not to touch his scar. Nobody touched his scar. There was something raw about it that had always lingered. It was as though Mai might touch the mark and her own beauty would be somehow marred – it was a dangerous scar. Zuko couldn't let her do that. It was too evil a mark for anyone to touch.
"I'm sorry," she'd murmured, turning away. She hadn't even thought of what she was doing.
"Mai," Zuko said again, taking her hands. The simple act of saying her name meant don't apologize. I love you. He pulled her close again and she put her arms around his neck. He lifted her up and laid her on the bed. He kissed her lips, her eyes, her cheeks, her neck . . .
"Mai," he whispered to her.
And now there he lay, thinking of how he couldn't let his wife touch his scar – how only one person ever had, many years ago.
Zuko didn't blame her for hating him. But he felt strange and different, trapped in the caves with her . . . He could suddenly remember with startling clarity fighting time and again, all across the world . . . how he'd taken her necklace – the one relic she had of her mother, he knew that now . . . he'd called her peasant. Spat the word out. Deemed her inferior because of her birth . . . well, look where his own birth had landed him . . .
She told him that his was the face of the enemy. He loathed himself then, something he'd never felt before. He was always angry at someone else, putting the blame on someone else's shoulders – his father, his uncle, his sister – anyone but himself. And somehow now she'd changed this. Showed him who he was. What he'd done. Told him what his uncle had been too kind to say.
He owed her, at least, his honesty.
He told her what the scar had meant. He'd never told anyone. But he could see in her blue eyes that she understood.
So when she approached him – said she could free him of his mark – it was as though she had told him he could be new again. He would be free. She stepped close to him, brought a graceful hand up to his face, and he had closed his eyes, yielded for the first time . . .
For a moment, he felt her cool fingers on his skin, on his scar, bringing with them a promise . . .
But then there had been a great rumble and a crash, they turned to look, she took her hand away, and the moment was gone.
It wasn't that he was in love with her.
It was that she had changed him. She'd promised to heal him. And he had betrayed her.
He became a coward when the time had come for him to decide.
Scarred was all he knew how to be.
He hadn't lied, though.
I thought you had changed.
I have changed.
His scar had changed from a mark of abuse and banishment to a mark of cowardice and shame. Too cowardly to fight back. Too proud to accept help when he needed it the most. He'd always been that way. Had he been brave enough that day, the world would have been different. Lives would have been saved. But he was too selfish and afraid to accept such change in himself. He deserved the mark now.
He never told anyone the extent of what had happened in the catacombs. Not even she knew how much she had changed him.
Zuko took his wife's hand and kissed it. He loved her. But there were some things, he thought, that she would never know.