Zuko is a prince. And like every prince, he knows himself. He knows his deepest desires and his darkest secrets. He knows what he wants and what he needs. And Zuko needs to regain his honor.
That's his mission. His focus. Every waking and most sleeping moments are spent trying to find the Avatar. But in the three years since Zuko's begun his search, he hasn't seen any clue as to the Avatar's whereabouts. He's starting to lose hope.
Zuko doesn't know that the Avatar, the Airbender everyone's looking for, dies in a storm one-hundred years ago. He doesn't know that the moment Aang dies, a little girl named Hama is born. He doesn't know that Hama learns to Waterbend and fights off the Fire Nation until she's taken. He certainly doesn't know that Hama dies after a failed escape attempt at the age of thirty, never knowing she's the Avatar.
When Hama dies, a child is born in Ba Sing Se. Zuko doesn't know the child is named Ming. He doesn't know Ming lives a happy life, for there is no war in Ba Sing Se, and learns to Earthbend recreationally. He doesn't know Ming dies at the age of fifty-three after a sickness takes him.
And he doesn't know that the moment Ming takes a last breath, a child in the Fire Nation takes their first. This is where Zuko's story begins.
In another world, perhaps Zuko might have seen a beam of light shoot up from the ice fields in the South Pole. As it is, in this world he sees nothing and retires to his room early, bidding his uncle good-night and ordering the crew to stay put for few days, just in case.
Zuko falls asleep quickly. He's trained himself to. It won't do for him to not be able to, especially since sleep is a luxury with his uncle's snoring. He needs to take it where he can get it.
When Zuko wakes up, he's no longer in his cramped room, but instead in the middle of a beautiful grove, surrounded by a tall temple. For a moment, Zuko thinks he's alone in this dream.
"Hello," a soft voice says.
Zuko whirls around, standing up and settling into an offensive stance easily. He's prepared to throw fire at this stranger, dream or not.
The stranger is a child. He's not expecting that. Zuko relaxes his stance. His eyes slide over the boy, drinking in every detail. The boy can't be more than thirteen. He's bald with a large blue arrow tattoo covering his head.
"Who are you?" Zuko asks warily. Somehow, he knows this isn't simply a dream. Something has changed. It's a sudden change, but a change he notices. The boys he's seeing is real or was real.
"I'm Aang," the boy says.. "And I'm the Avatar. Or I was, at least." The boy's head is hanging, but his whole visage says he's hurt. And resigned. "I'm sorry."
"For what?" Zuko asks heatedly. "Where are you? What do you mean?"
"I died, Zuko," Aang says, looking up at him with big, sad eyes. "One-hundred years ago."
"But that means that I've been looking for you when I should be looking for someone from the Water Tribes or the Earth Kingdom!" Zuko exclaims. "This whole time!"
"You're right," Aang says. "There were others after me. A Waterbender named Hama. She never knew she was the Avatar. She died when she was thirty. Then an Earthbender named Ming. Ming never even knew about the war or that he was the Avatar. Ming died at the age of fifty-three."
Aang looks sadder now, more than ever. Zuko has a strange feeling building in his gut.
"They never found out, so now it's my job to make sure the next Avatar knows so they can end this war," Aang says.
Suddenly Aang's eyes harden and he looks determined. It's a far cry from the scared, sad boy he was a moment before. Everything goes cold in Zuko's mind. Because suddenly it makes sense. What Aang is trying to say. Why ever since Zuko turned sixteen he's felt strange and broken.
"Zuko," Aang says seriously. "You're the Avatar."