Disclaimer: I do not own Avatar: The Last Airbender

Author's Note: I blame MyrmidonGuy for this. I never knew my muse took orders before. Anyway, this idea came to me a while ago, so it's rather AU now and likely to become more so. It is essentially canon through Return to Omashu. I begin with a few "missing scenes" from that episode and then go off from there. I also assume that the events from my one-shot After the Cave have occurred, but it's not necessary to read that to understand this.

I have not seen every episode, so I apologize in advance for any inconsistencies.

Omashu Revisited

Aang, the last airbender and current Avatar, walked the spirit world, looking for someone. Since he and his two friends, the waterbender Katara and her brother Sokka, had to wait until full dark to sneak into the city of Omashu, he had decided to go to the spirit world and ask a question that had been bothering him.

"You seek me, young Avatar?" Suddenly Roku, the most recently deceased Avatar, stood before him. Aang bowed to him respectfully.

"Yes, Avatar Roku. I have a question about the Avatar State. You told me that it would only take over when I was in mortal danger."

"True."

"But there have been two times when something else triggered it. I don't want it to ever happen again, but I was hoping you could explain the reason."

"Well, tell me about these two times." Avatar Roku began walking thoughtfully, and Aang moved to keep pace with him.

"The first was at the Southern Air Temple, when I saw…" Aang trailed off. Even in spirit, he found it difficult to put into words. At last, he managed to utter his mentor's name. "Gyatso dead. Then this last time, the Earth Kingdom army was attacking me, but that wasn't enough. Only when Katara's life was in danger did I go into the Avatar State."

"Ah yes," mused Roku. "I think I can explain. When you love someone, that person effectively becomes an extension of yourself. In many cases, you may even find that another's safety means more to you than your own."

Aang mulled this over. He had certainly loved Gyatso; he was the only father Aang had known. Aang had definitely felt like a part of him died the day when he discovered that Sokka and Katara were right and his people truly had all been wiped out. But that meant….

"I love Katara?" Aang exclaimed in surprise, stopping suddenly. Roku turned to look at him.

"Of course. Didn't you know?"

Aang considered, thinking about all of the things he felt towards Katara, whether she was present or absent, and tried putting the umbrella of love over them all. It seemed to fit.

"Yeah. I guess I did." He paused again. "Does it have to feel so awful?"

Roku laughed, the first genuine laugh Aang had ever heard from his predecessor. He wondered what was so funny.

"Yes, it is awful, and wonderful, and beautiful, and terrible," Roku said when he recovered. "Love comprises the best and worst of everything that makes us human. Like the Avatar State, it provides both great strength and great vulnerability."

"Does she love me?" Aang wanted to know.

"That is something you must discover on your own."

Aang nodded. He had expected as much, but he'd had to ask.

"Allow me to give you some advice before you go," Roku added thoughtfully. "Accept the strength of your love, but be ever aware of its weakness."

The two Avatars, joined through time, bowed to each other, and Aang returned to his body.

When he opened his eyes, Aang saw his friends, Katara and Sokka, sitting near him, facing outward. They were trying to appear casual, but Aang could see the subtle alertness in their postures. He smiled a little to himself at their protectiveness. Ever since Prince Zuko had captured Aang's body while his mind was elsewhere, the siblings had been more watchful over his ventures into the Spirit World.

Aang wanted to take a moment to look at Katara in the light of his new understanding, but he knew they would soon notice he was moving, so he set that aside for now.

"Hey, I'm back," he said instead. The others turned toward him.

"Hi. Did you get the answers you needed?" Katara asked.

"Yes," Aang answered, not elaborating for obvious reasons. Katara looked like she wanted to press further, but she was too polite to do so. As usual, Sokka was not very interested in anything spiritual and was preparing for action.

"So, can we go now?"

"Yeah," Aang nodded. "There's this secret entrance…"

Aang led them up the sewer system into the city, eventually stumbling onto the underground resistance (pun intended). Sokka came up with the brilliant idea of getting everyone out of the city by making them all appear to have a kind of plague. When they were nearly done applying the sewer suckers to the Omashites, Aang noticed Katara pulling one off of a young man.

"What's a pretty girl like you doing in a place like this?" the Earth Kingdom man asked her. It was an old line, but it had the desired effect – Katara blushed faintly and looked away.

"It's a long story," she replied shyly.

"I'd like to hear it sometime."

An irrational surge of jealousy rushed through Aang; one hand tightened around his staff while the other curled into an involuntary fist. Before he could even think about acting on his feelings, though, he felt a restraining hand on his shoulder.

"Steady," Sokka murmured above him. "I'm her big brother; this kind of thing is my job."

"You don't understand." Aang angrily tried to shrug off the hand, but the young warrior's grip only tightened.

"Actually, I do."

Taken by surprise, Aang looked up and saw in his friend's blue gaze the pain of lost love, along with a kind of sympathetic understanding. Aang faced front again, confused.

"Does she know?" he whispered.

"Nah," Sokka replied, finally removing his hand from Aang's shoulder. "Although how she can miss it is beyond me."

"Unless…she doesn't want to see it."

"Hey, don't think like that. I mean, I didn't think Princess Yue would ever look at me…" he trailed off.

"I'm sorry about Yue," Aang said after a pause. Although he had not been there, he had heard what happened to her. Sokka nodded curtly.

"She made the right choice," Sokka admitted. "She did her duty. And I have to do mine."

This last part was added almost to himself. Aang turned back to him, wondering exactly what he felt his duty was. To his sister? The Avatar? The world? This opened up a lot of questions that Aang wasn't certain he wanted to pursue. At last, Sokka shook himself and spoke to Aang again.

"You go, do what you need to. I'll keep an eye on this situation."

Aang nodded, took his leave of Katara, and began to search the city for King Bumi.

When he rejoined the others later, unsuccessful, Katara gave him a sympathetic hug. Unfortunately, Aang was almost too worried about his old friend to notice. Shortly thereafter, the message arrived confirming that the Fire Nation representatives had King Bumi and would exchange him for the baby who had inadvertently become part of the refugee group.

Some time later, Katara had fallen asleep on her side with the baby resting on her arm. Aang smiled at the two of them. She would have a sore arm when she woke up, but right now, they looked very peaceful.

"Are all girls like that?" he whispered to Sokka.

"Like what?"

"You know," Aang gestured to the sleeping pair. "Good with babies."

"I don't know. I guess," Sokka shrugged, not very interested. He looked like he was about to try to sleep also, but Aang was too concerned and wanted the company a little longer.

"Have you ever thought about having children?" he asked the older boy.

"No, not really." Sokka leaned back against Appa. "I guess you don't have much choice, though, right?"

Aang blinked, confused.

"What do you mean?"

Sokka turned to look at him in surprise. Apparently satisfied that the young Avatar really didn't understand him, he answered.

"Aang, you're the last airbender," he said patiently. "If you don't have children, there won't be any more."

Sokka waited as this sank in. Aang's eyes widened as he grasped the situation.

"Which means the line of the Avatar will end!" he realized. The full import of this gradually filtered through his consciousness. Not only would there be no airbender to be born an Avatar in the next cycle, but the three Avatars in between would have no airbending master to learn from and therefore would not reach their potential. "Great. No pressure."

Sokka laughed, though whether at Aang's predicament or his expression, Aang couldn't be sure. Then Sokka did his best to reassure his companion.

"Hey, you've got plenty of time. Let's get this saving the world thing out of the way first. Then you can start thinking about raising a flock of airbenders." He looked over at Aang slyly. "And maybe one or two waterbenders."

Aang's eyes darted over to him briefly, and he could feel himself flushing. At least, in the dark, he hoped Sokka couldn't see that.

The following day, after the botched exchange and the ensuing battle and chase, Aang sent his friends ahead while he returned the baby to the governor's family. He was gratified to see that they were genuinely pleased to get the little boy back.

Aang found Katara and Sokka just after sunset, some distance away from Omashu in a forest clearing. They were already setting up camp and trying to decide where to go next. Katara greeted Aang with a smile that warmed him from the inside.

"Were they happy to have him back?" she asked, handing him a piece of fruit. Aang bit into it and nodded. Apparently, the siblings had decided not to have a fire, either due to the lateness of the hour or the proximity to the occupied city. However, they had lit two lanterns to ward off the approaching dark.

"Very happy. They didn't even care how he got there."

"Maybe there's hope for the Fire Nation after all," Katara said.

"They're not like their daughter, apparently," Sokka commented from where he was putting up the tent. "What kind of sister is she, anyway?"

"For the record, I'd never give you up that easily," Katara informed him.

"Same here, little sister."

Katara raised her eyebrows at the "little sister" bit but decided to let it pass. Aang grinned at his two friends. It was nice to know that, despite their frequent bickering, they loved each other.

"I think something went wrong with the noble houses of the Fire Nation in the last few generations," Aang said. "I don't remember anything like that before."

"I don't know, Aang," said Sokka. "There must have been something weird about the Fire Lord even then. That kind of thing takes time to establish itself in a family."

"Besides, wasn't he the one who started this war?" Katara put in.

"And didn't we hear a rumor recently about Zuko's sister?" Sokka asked.

"Yeah, that she tried to capture him or something," Aang answered. "To be honest, I never met the Fire Lord from 100 years ago."

"Model family," Sokka said sarcastically, shaking his head.

"Indeed, the royal family is, perhaps, not the best example," came a new voice. Everyone turned to see Prince Zuko and his Uncle Iroh approaching on a riding beast.

Author's Note: Surprise! I will be putting some things in this fic that I predict will happen in the series eventually. I'm just accelerating things. In addition, in case you haven't guessed, I will also be injecting some of my philosophy and interpretations. I will be using Toph as the earthbending teacher because I didn't have a pre-existing idea for that character.