A/N: This chapter. I really hope you enjoy it, because it's the beginning of our first set of...well, adventure-esque happenings. Not that the last chapter wasn't the realy start, but...well, you'll see. So. In case anyone was wondering: stuff happens! Exciting, huh?

I hope you'll excuse the unfortunate mixture of instruction and suspension in this. I know, I know, it's an horrible juxtaposition, but it had to be included. I tried various ways to get around it, and none felt quite right, so I settled for a lot of character jumps and I tried to make each part worthwhile. I'll try to do better in the future to not include such separate themes in the same chapter, since it's kind of mood-killing.

And...well. I don't have a random fact/story to include at the front of this, as seems to be my norm. Oh, question: should I create chapter titles? Please leave an answer in a review, if you feel so inclined...and enjoy!

"So. Firebending."

The brunette siblings looked at each other and nodded.

Zuko cleared his throat. "The...er, bending of fire."

Another simultaneous nod.

"We...we can control fire. Like this." Zuko demonstrated creating a small flame and shooting it up, high into the air.

Nod.

This was worse than it had been trying to join the Avatar's group two years ago. When he had tested his greeting skills on the toad. Because, unfortunately, he still remembered that toad and its unhelpfulness.

With Aang, he felt as though he himself was learning at the same time; they had both had to master the dragon's methodology together, a fact they kept secret with pride.

But with Tai and Kari Kamiya, who had never heard of Firebending before this excursion, it would be different.

They had traveled outside of Ba Sing Seh. Zuko had decided the safest place to practice Firebending was outside of the city's walls; even if the city was made of stone, he knew the danger of beginning the lessons, and he wasn't going to risk harming anyone. In the background, Mai was sitting on a nicely-placed stone, holding Zuko's Mokumon a little away from her body-he had a drooling problem whenever he got excited, which was most of the time. Her own Mokumon was crawling around the dirty ground, making cooing noises randomly.

He was slightly amazed that he could tell them apart, but his own was familiar, already; hers was...well, different. Even though they were all but identical. Maybe there really was something about them being partners.

"So. When you Firebend, you need to be in touch with your passion," Zuko said, trying to remember what it was like the first time he ever Firebent. It was hard; that was a long time ago. "It comes from inside you, and you just need to let it out; you know that you won't get burned."

"Can Firebenders get burned?" Tai interrupted. Kari rolled her eyes at him, and Tai seemed to realize what he had said; his eyes focused, briefly, on Zuko's scar.

Zuko cleared his throat. "Anyway, you need to control your Firebending. It's considered the most dangerous of the elements. For obvious reasons." He stopped for a moment. "Do you understand?"

The two nodded.

This was going to be a long day.

He had tried to make Iroh do the teaching; at least, to make him do the basics. His uncle had agreed, but he had to mind the tea shop in the morning, as people left their homes to take to the busy streets once again. He promised he'd head over to their training area after the lunch hour ended, but that wouldn't be for some time yet.

So it was Firelord Zuko's job to teach them the basics.

He would have recruited Aang to help out, but the Airbender had decided to go on a flight with Sokka. Apparently, he had wanted to visit with Appa, who hadn't been flying for a while.

Zuko wished he had joined them.

They had had an impromptu meeting in the morning, courtesy of Katara and Sokka. There, in the morning shade of Iroh's garden, the Waterbenders had explained about the strange events of the previous night. Zuko suspected that was another reason Aang had gone flying today. He would find someplace quiet and contact the Spirit World, with Sokka guarding his mortal body.

Not that the Digidestined knew any of this. The Firelord was pretty sure that they didn't have common spirits in their world, which was an uncomfortable thought.

"How about we begin with an exercise on focus?" Zuko wasn't sure if the drill would be to help his pupils prepare themselves, or to help himself clear his busy mind.

"Why are we up here?"

"Because Appa wanted to go for a flight," Aang answered simply.

Sokka yawned and stretched. "But why are we up here? Appa doesn't need you to fly." He fingered at something caught in his teeth. "Isn't the story that the air bison taught Airbenders their stuff?"

"Appa was lonely."

"Oh, so you speak bison now."

"Sokka? Stop talking." Sokka put his hands up in concession and started rifling through his satchel. Aang sighed. "I don't want to go to the Spirit World in the city. There's too many distractions." He wasn't sure why he felt like that was a lie. It was true; the Earth Kingdom capital had too much noise...

Aang reached down to pat Appa on a horn. "Good job, buddy. Good flying." They were soaring through the sky, over Ba Sing Seh, now over the rocky land surrounding it.

Sokka had taken out his Digiegg and was twirling it gently around in his hands. "I wonder if Momo could fit in this shell."

"...that's random..." Momo was perched on Aang's shoulder. He had been avoiding the Digidestined for the most part, and didn't seem to trust the baby Digimon that had appeared.

And what Momo didn't trust, Aang didn't trust either.

"I know. I'm just wondering out loud. Ignore me."

If only Aang could. "Why did you bring the egg with you, anyway?"

"So I can make an omelet while you're all spirit-sensitive," Sokka said sarcastically. "Look, it's kind of boring just staring at you aglow and everything, so I was going to hatch it."

"Oh." Aang felt a little betrayed-but he never said that Sokka had to spend his time staring him down, when he went to the Spirit World. That would be awkward, and unfair. "Good luck, then."

"Thanks."

They fell into a comfortable silence, dominated by the chilly wind. After a few more minutes, and a bit of cloud-hopping on Aang's part to get rid of some of his tension, they landed in the shade of a large boulder. Appa roared gently and plodded over to a clump of yellow shrubs, which he promptly started sniffing and tasting. Momo flew to the top of the boulder, as though he himself were going to keep watch.

Aang settled himself on the ground. "Are you certain that man said the Spirit World was in trouble?"

"Yeah. He seemed frantic." Sokka was dusting off a stone to sit on.

The Airbender nodded. If Sokka was sure, then there was no way around it. He didn't want to go to the Spirit World-the others never seemed to understand how insecure and dangerous it was in there-but he had a duty, to protect it.

The Avatar put his knuckles together, and as his spirit left his body, his blue tattoos began to shine.

Tai yawned as covertly as he could. Not that it was easy hiding a yawn, but he and Matt and been working on it, during long and often dull class sessions. They might not hang out as much as they used to, when the memory of their first adventure had been so fresh, but they still managed to understand the need for a diversion in the face of a boring class. And staring contests were strangely entertaining.

So he muffled his yawn, wishing he could do something to shake away his tiredness.

But that wouldn't exactly be focusing, would it?

Zuko had instructed him and Kari to stare at the fire he himself was holding. Just to stare. Not to try to control it, or touch it, or even do anything to it. Just stare, and relax without losing focus.

It seemed a little late for that.

Tai chanced a glimpse at his sister, standing next to him. She was staring intently. Or, rather, calmly.

Tai had to give her credit: he doubted she had even lost any focus yet. Well, she was always better at paying attention quietly.

He jumped when she stood straight and looked at him.

Too late, he realized his mistake-Zuko had extinguished his fire and motioned for them to relax. And Tai, not noticing, was still crouched as though he were paying attention to the now non-existent fire.

Zuko cleared his throat. "Good job, Kari." He didn't say anything to Tai, much to his annoyance. "Take five minutes, and then we'll try again." The Firebender walked toward Mai.

Tai shook himself, stretching his tense muscles. "Well, that was fun," he said sarcastically. Kari half-smiled at his tone.

"It's not too bad."

"You're kidding. We were staring at that fire for twenty minutes. What was the point?"

"Maybe to adjust our eyes for the brighter light?" his sister asked. "And to make sure we can focus enough to keep control of our fire when we make it ourselves?"

"Sure, sure. I'd just rather do the staring on a padded seat."

Kari giggled and rolled her eyes.

"Hello?" His call echoed throughout the still world. "Anyone?"

Nothing.

Aang jumped down from the boulder he had awoken on and looked around. There was no sign of life, as far as he could see, but he didn't focus on that. The spirits didn't always appear when he first arrived. They rarely did, to his annoyance. He'd have thought they would have looked forward to the living connection to the other world arriving, but that reception never really occurred.

He wished Roku would appear. He tended to make more sense than most of the other spirits; they just gave him headaches with their riddles or demands.

Actually, he was starting to get a headache-there was a strange humming sound in the background, something he had never heard before, that wouldn't go away.

Strange plants littered the rocky ground. Aang looked at a few of them; one appeared to be breathing, expanding and contracting at regular intervals, letting off a pungent scent. When its bud opened up and let out a keening, hissing sound, he backed away and decided to find something else to explore.

"It's me, the Avatar. Any problems here?"

There was no one here to have problems, but Aang decided not to mention that. Maybe they were invisible or hiding.

"Is anybody here?" he called out, cupping his hands around his mouth. "If not, I'll just be going..."

"Aang."

The boy-the teenager, really-turned around quickly. "Roku!" His predecessor was staring at him, his dragon companion curled close to the ground, smoke rising from its nostrils. "Thank goodness! I've been meaning to talk to you, and...why do you look so..."

The word wouldn't come. Because Roku didn't look normal. And Aang was pretty sure it wasn't natural.

Roku was flickering. Green and red dots appeared frequently across his shape, and hazy pieces flickered in and out of view constantly. It was as if his image wasn't able to fully form, was struggling to take its actual shape. The dragon was the same way.

"Aang," Roku said. Even his voice sounded strange, as though a voice could be full of holes. The sound seemed covered in strange popping noises. Like the hum that surrounded them. "The Spirit World is in danger."

"What's going on?"

"I'm not sure." Roku didn't look ashamed to admit that; he just looked sorrowful. "Something seems to be invading."

"What? Something's invading the Spirit World?" Aang blinked a few times, waiting for Roku to deny it. He didn't. "Is that even possible?"

The older man decided not to answer that last question. "Things are flickering, appearing and disappearing without relief. I fear if this continues, it will seep through the cracks and into the living realm."

"What can I do?"

"You'll need to find the cause and stop it."

Because that was always so easy. But Aang didn't have a choice. As he watched, Roku was fading in and out of view.

Mai handed Zuko his Mokumon. "How's it going?"

"Do you want to take a turn?"

Mai chuckled drily. "You're doing fine."

"I don't know what I'm doing," Zuko admitted. "Beginning Firebenders usually go through extensive mind training before we even touch flame, but that doesn't seem appropriate, especially when Tai's almost our age."

Mokumon was making putting noises. It seemed to want to talk, but didn't know how. Did Digimon talk? That would be different.

"Just do what you need to teach them. They don't seem especially stupid; at least, the girl doesn't. I'm not sure about the boy."

"He stopped paying attention almost immediately," Zuko admitted, rubbing his forehead.

"I can't blame him. I stopped paying attention before you even started."

That was what was good about Mai; she didn't lie or pretend things were what they weren't. "So I should just have them start on fire? Even though they could seriously hurt someone, or themselves?"

"Do you think they will?"

"It could always happen. Even I could hurt someone I hadn't intended to."

Mai rolled her eyes and stood up from her rock. She looked straight down at her own Mokumon. "And what are you doing?" she asked it, raising an eyebrow. "What do you think? Should Zuko teach them Firebending?"

"Mai?" Zuko asked his girlfriend. She was talking to something that couldn't talk back; surely she realized this.

However, the girl just crossed her arms and stared at it. It stared back, mewling happily.

After a few moments, she turned back and looked at Zuko. "It has a flame on its head, doesn't it?"

Well, yes, both of the Mokumon did. Zuko's Mokumon had a larger flame; Mai's one's was barely a spark compared to his. But Zuko had felt the heat whenever he picked the smoke-ball up.

"Do you worry about it burning you?"

"Well, no, not really..."

"Why?"

"Because...it wouldn't hurt me intentionally..."

Mai nodded. "Look, Zuko. I don't trust these Digidestined. Not at all. But I don't think either of those two would do anything dangerous when they could hurt each other just as easily as one of us. At least, not intentionally."

She shook her head. "Now I'm going to go on a walk. Have fun with focus training or Firebending. It's your choice, really."

Sokka kept watch for about five minutes before turning to his egg.

After all, if something was going to interrupt them he'd see it from a mile off. The ground around them was flat and empty of anything besides the occasional boulder, and the city wall in the far distance. If he didn't notice it immediately, he could trust Momo and Appa to alert him.

Aang was glowing and breathing slowly. All good on that front.

So. The egg.

Sokka hated to admit it, but he was just a bit curious about what his Digimon would be. There were two of those little smoke-cloud things; there were Katara, Suki, and Toph's blobs. They were all cute, actually, even if Toph's Zurumon also had an evil little glint in its eyes. Toph had laughed wickedly when he had mentioned it to her.

What would he get? Maybe his would have spikes or something. Or fangs. That'd be pretty cool. And then he could properly tease Zuko for having such an innocent little thing when his Digimon was epic and dangerous.

But if his was cute, he wouldn't complain too much.

He hesitated for a split-second more. It was Momo's smug gaze that finally made Sokka grab the egg and start ferociously rubbing it.

He was glad that no one could see his expression right then. It probably wasn't appropriate for a Water tribe warrior.

The egg let off a small hiss and a pop, disappearing in a cloud of pleasant-smelling smoke. Where it had sat on his lap was now a little purple ball of fuzz. It slowly blinked open black eyes over its white muzzle and, looking up at Sokka's excited expression, it opened its mouth-fang free-and squeaked.

There was a flash of blinding light. Aang instinctively covered his face with his arm, waiting a moment before looking up.

Something had happened. The very air seemed to be sputtering with little black-and-white dots, more ferociously than before.

Roku was still in front of him, but his entire form was flickering more rapidly, and the dragon had disappeared.

"What was that?" Aang asked urgently.

The older Avatar shook his head. "That's the sixth time. Whenever that flash occurs, more of the world is infected by this...this...disease. This virus."

"Do you think there's an object or something that could act like a medicine, then?" There had to be something. This wasn't natural, and Aang didn't want to think about what would happen if it continued.

"I'm not sure, Aang, but you need to try to find something. I'll try to figure things out on this side and send you a message, but I'm not sure if that's possible at this stage."

For the first time, Aang felt as though he was the older incarnation, a strange thought when the older man had died before he had even been born. Or that Aang had been born because Roku had died. "I'll do whatever I can. I will fix this."

"Of course," Roku nodded. He started fading away, a mix of natural spiritual mysticism and the strange flickering. "Good luck. We'll be counting on you."

Aang blinked as mist swirled around him, the black specks infecting it as well. When he opened his eyes again, he was in his own body.

Sokka was chasing after a purple Digimon, who was in turn chasing after Momo, who was climbing on top of Appa for safety. Appa simply yawned.

They had no idea the danger the world was in.

And Aang was responsible for saving it.

When Zuko called them back for training, Tai groaned. "Okay, if this is just more concentration…"

"It's not."

"Oh. Okay," Tai finished lamely. This guy could get along with Matt; neither liked to talk much.

"We're going to start actually creating fire," Zuko said. Tai jumped up and stood next to him; Kari stayed at her position on the ground.

"What do we do?" the Digidestined leader asked eagerly.

Zuko explained. How to capture the fire and pull it out. How to make it appear; how to control it.

Tai listened. He would do this. And then he could show Agumon a thing about creating fire.

"Now, try. Like this." Zuko made a strange motion with his arm, then extended it rapidly forward. Fire burst from it, disappearing a few feet away. Zuko straightened and looked at Tai expectantly.

Grinning, Tai cracked his knuckles. "Piece of cake." He imitated Zuko, and shot his hand out like he had done twice before.

To a different result.

"What?" Tai blinked. Nothing had appeared. "But…that's just unfair…"

Zuko raised an eyebrow. "That happens sometimes, while you're learning. Try again."

But Tai never got a chance to try again. Because, at that moment, something landed heavily, a foot in front of them. Rocks and dust exploded upward. Both boys looked around.

A glint in the distance. Something solid, and metallic. Zuko squinted; Tai quickly pulled out his spyglass and looked toward the shine and the rising dust. "It…wait. I can't see it clearly right now. But there's at least two or three of them, and they're coming quickly…"

Kari stood up.

Tai was still trying to see through the dust. "Three, and…they're like vehicles…but this place doesn't have cars…"

It was at that moment that the first of the three shapes shot at them again.

"Down!" Tai shouted, pulling Kari to the ground beside him and hoping that Zuko also heeded his warning. He didn't have time to check, because, at that moment, a scattering of giant rocks crashed to the ground, feet from where they had been standing. "What's going on?" he asked, jumping to his feet.

"How would I know?" Zuko shouted back, moving next to him, squinting at the smudge of dust that hid the attackers.

"You're the Firelord. You have power here, right? You should know what's going on!"

"Not 'here.' In the Fire Nation. This is the Earth Kingdom." Which sort of explained the attack with boulders. But not why they were being attacked.

Tai looked up again, then immediately rolled to his right, pushing Zuko to the left. Another boulder fell where they had both been laying.

"We need to get out of here. Kari!" He looked behind; his sister was crouched low to the ground, covering her nose from the dust. She looked up at his call. "Get back to the city! Now!"

"But…"

"I'll be there in a moment. Go on!"

Kari didn't look happy with the command, but she didn't argue; crouching low, she started running back toward the city and the gate, dodging already fallen rocks.

Zuko was standing tensely, glaring at whatever the enemy was. "We need to stop them."

"What, does fire actually hurt machines here?" Tai sounded excited at the prospect.

"Well, no, but…"

"We need Earthbenders. Or Waterbenders. Or freaking Airbenders. I don't think us two will do much damage to a metal shell," Tai said quickly. "But…" He wanted to fight, though. He hadn't been part of a good fight in…well, in three years. And he wanted to know why they were being attacked, in the middle of a good day.

Zuko spoke, a contemplative note in his voice. "There has to be people inside those machines…doing the bending and controlling the machine…"

Tai grinned. "We should probably stop them from reaching that wall, right?"

A nod.

They might have proceeded, even with Tai's words of wisdom, even with Zuko's beneficial years as ruler of the Fire Nation, if a yell hadn't interrupted them. "I leave for five minutes, and you get someone to attack you? Typical."

"Mai," Zuko blinked, and then the two boys were running toward her and the Mokumon. As more rocks started to soar through the sky.