This is an idea I had before Journey to Ba Sing Se and decided to write it up while I'm working on the sequel. It's not in the same story arc.
In this Aang didn't unmask Zuko when he was shot by the Yu-Yan archer, instead (upon seeing blood) took him to the herbalist's place to recover while Aang went back to make sure Sokka and Katara were ok.
Zuko woke up with a groan. His head throbbed painfully. He put his hand up to hold it and found a thick bandage wrapped around part of his head. He sat up, feeling woozy, trying to get his bearings. He appeared to be on some sort of table, in a house full of plants.
Zuko rubbed his eyes. It looked like someone's garden, only with a roof. A medicinal scent reached his nose. A herbalists then, Zuko nodded to himself, then winced as a fresh wave of pain washed through his bandaged head. He managed to stand, but had to hold tightly onto the table until the world stopped spinning. A meow startled Zuko and he immediately went into his Firebending stance and just as quickly regretted it.
A white cat ambled up to him, meowing at him in confusion. Zuko stared back at it, wondering if it was a trick of his mind.
"Miyuki," an old woman's voice called out, scolding, "Are you bothering the patient again?"
The owner of the voice appeared in the doorway. The cat gave a haughty meow and jumped onto the table, its tail held high.
"Ah," the woman said, noticing Zuko standing up, "You appear to be on your way to recovering quite nicely."
"Where am I?" Zuko demanded.
"This is an old herbalist institute," the woman answered, picking a few leaves from a plant and putting it into a bowl, "There used to be others, but they all left a long time ago. Now it's just me and Miyuki."
Zuko made a noise of frustration and pushed himself away from the table. He didn't make it two steps before his legs gave way and he crashed to the floor. The old woman made a tutting noise, but finished adding leaves to the bowl before helping Zuko to his feet and back onto the table again.
"Sit still now," she said, "These herbs work wonders for healing head injuries, but they do tend to leave the drinker a little weak."
Zuko touched the bandage on his head again. He closed his eyes to remember clearly. He'd gotten the Avatar out of Zhao's clutches. They were a good distance from the fortress when... nothing. All Zuko could remember was pain and a flash of light. He had no idea where he was or how he'd gotten there.
Zuko opened his eyes as a cup was pushed into his hand. The old woman began clearing the bowl and used leaves away. She frowned at Zuko when she was that he wasn't drinking.
"Drink up," she ordered, quite forcefully, "You'll never get any better if you don't."
Cautiously, Zuko gave the contents a sniff. It didn't smell any worse than Uncle Iroh's tea. The old woman gave a smile as Zuko tentatively sipped at the liquid.
By the time he had reached the bottom of the cup, Zuko was feeling drowsy. He lay down on the table, intending to just rest for a moment...
The sunlight streaming through the cracks in the roof told Zuko that he'd been out for some time. He sat up slowly, having learnt his lesson. His head still throbbed, but it was duller now. Zuko froze as he heard voices, familiar voices. However, Zuko couldn't place them.
"...wakes up," said one voice, it sounded like a child, far too high and excited to belong to an adult.
"Maybe he can help us," that voice belonged to a girl, "Another warrior would be useful, especially if he complains less."
"Hey!" said a third voice, a boy like the first, but this one sounded older, "I don't complain that much." There was the sound of metal blades sliding out of a sheath, "Nice swords though."
Zuko got to his feet at those words. Those swords were his, and no one was going to mess with them. Clutching heavily at the table and plants, Zuko made his way to the door frame. He held it firmly as his eyes took in the scene.
A boy – Water Tribe, and not much younger than Zuko himself – was admiring Zuko's broadswords. The girl – also Water Tribe – had frozen in shock as she caught sight of Zuko. The other boy – a bald kid with an arrow tattooed on his head – was holding Zuko's Blue Spirit mask and smiling at the Water Tribe boy.
Arrow. Airbender. Avatar.
Zuko punched a blast of flame at the Avatar with a snarl. At least, that's what he meant to do. Instead, a pathetic wisp of smoke was all that his forceful movement had produced. Without the support of the door frame, Zuko's knees buckled and he only just managed to catch himself before his face hit the floor. Undeterred, Zuko tried again, with the same result. His breath was coming in short pants now.
The other three in the room dropped into fighting stances, but none of them was willing to attack the ill Firebender. Zuko's head was swimming, but he forced himself to listen to what the Avatar and his friends were saying.
"...rescued you?" the Water Tribe girl asked, her voice skeptical, "Him?"
"I... I guess so," the Avatar sounded unsure.
"Yeah, right," the Water Tribe boy snorted, "He's probably just pretending to be whoever this Blue Spirit guy is."
Zuko had been concentrating on getting his breathing pattern back to normal, but at the Water Tribe boy's words he tried another attack. This one failed to produce any fire like before, but did gain him ground. Zuko's hand landed on his Blue Spirit mask that the Avatar had dropped on his first attack. He frowned as he rubbed his fingers over the dent that hadn't been there before. It clicked into place and Zuko put his hand to his bandaged head.
"Yu-Yan archers," he muttered.
"Is that what those archers were called?" the Avatar asked.
Zuko's head snapped up and he winced against the pain. He scowled at the Avatar and at the throb behind his eyes. The Avatar drew back, his friends flanking him. This wasn't a fight Zuko could win, not in his current state anyway. Zuko bowed his head in an attempt to stop the throbbing.
There was movement from the group in front of him and a few muttered words. Zuko looked up as his broadswords were offered to him. The Avatar held them out without speaking. For a second, Zuko considered ignoring them, but he gave way to reason. He snatched his swords back and slung them over his shoulders. The Avatar backed off again.
Zuko struggled to his feet. He swayed and the Avatar was suddenly right there, holding him up. Zuko tried to push him away, but his limbs weren't obeying properly.
"Get off me," Zuko hissed threateningly.
The Avatar ignored him, instead asking the Waterbender a question. The girl moved to a nearby table and picked something up, not once taking her eyes off Zuko. She cautiously walked toward the Firebender and the Avatar, a cup held in her hands.
"The herbalist said you should drink this when you woke up," she said, offering the cup to Zuko.
He took it, glaring, and the liquid within started to boil. The girl backed off to where her brother was standing. He was the only one who hadn't lowered his guard yet, Zuko noted with grudging respect. Zuko forced his temper – and the tea – to cool and sniffed the cup. It smelt exactly the same as last time. Zuko downed it, wanting his head to clear.
His eyes felt heavy and Zuko could have kicked himself. He'd forgotten the tea acted like a tranquilliser. The mask slipped from his fingertips and the cup crashed to the floor. The Water Tribe siblings said something, but Zuko's foggy brain couldn't comprehend it. Despite the Avatar holding him up, Zuko's legs gave way and he lost consciousness as the ground rushed up to meet him.
Aang, Katara and Sokka stared at the sleeping Firebender in varying degrees of suspicion. Aang was the first to move, shifting Zuko onto his back so he wasn't laying on the shattered pieces of cup any more. Sokka was the second to snap out of it.
"Right," Sokka said, not lowering his boomerang, "Let's go."
"Wait," Aang said, still crouched next to Zuko, "We can't just leave him here."
"Sure we can," Sokka said, determinedly, "Let's go."
"No," Aang said, standing up to look at his friend, "The herbalist told me that Earth Kingdom troops sometimes come by this way. If they find him here, they'll kill him."
"So?" Sokka asked.
Aang pulled Zuko up and started to drag him outside. Katara helped by taking the other side of the Firebender. Sokka sighed and followed them, picking up the Blue Spirit mask on the way.
"Are you sure this is a good idea, Aang?" Katara asked.
"The monks taught me that life is sacred," Aang replied, "I'm not going to sit around and let someone die."
"Yeah," Sokka said, rolling his eyes, "This makes a lot of sense. Let's bring the guy who's constantly trying to kill us."
Aang took the Firebender from Katara and Airbended them both into Appa's saddle. Katara and Sokka walked up the bison's tail and sat on the opposite side of the saddle to Zuko. Aang took his customary position on Appa's head and flicked the reins.
"Yip yip," Aang said.
Appa flicked his huge tail and then they were airborne. Sokka examined the Blue Spirit mask for some time, before tossing it to Zuko's side of the saddle.
"I don't get him," Sokka said finally.
The third time Zuko woke up with a throbbing headache he forced himself to keep his eyes closed and his body still. Someone was unwrapping a bandage from around his head.
"I'll do it, uncle," Zuko muttered, "It's my fault."
The hands hesitated, but continued. Zuko's eyes opened slowly, blinking the world into focus. It took a moment to register that the worried face hovering over him wasn't that of his uncle, but that of the Waterbender travelling with the Avatar. Zuko scrambled away from her, wincing at the sudden movement. The bandage she was unwrapping had loosened and slipped over his scarred eye.
"What are you doing?" Zuko snapped, ripping the bandage off.
"Trying to help," the Water Tribe girl responded, sounding put out.
"I don't need your help," Zuko shot back.
The girl scowled and turned her attention to a pot of something sitting over a small campfire. Zuko looked around. They were in a small clearing, the thick foliage hiding them from anyone who might be looking. The Avatar's bison was taking up about half of the space, growling every now and then at the lemur chittering on a tree branch. The Avatar and the Water Tribe boy were nowhere in sight. With some relief, Zuko recognised the weight of his broadswords on his back. His Blue Spirit mask was laying on the ground next to him.
"Here," the Waterbender said, offering Zuko a bowl of stew.
When he didn't take it she put it on the ground with a huff, moving away to do something else.
"Where's the Avatar?" Zuko demanded.
"Looking for food," she answered shortly.
Zuko watched her straighten the tent lines. It didn't need doing, it just gave her something to do instead of looking at the Firebender. Zuko picked up the bowl of stew and tasted some. It wasn't bad, definitely not Fire Nation food, but much better than some of the Earth Kingdom food his uncle had insisted they try.
A roll of thunder sounded in the distance. Both Zuko and the Waterbender looked up at the heavy sky. It appeared to be a stormy season on the Earth Kingdom coast. The Water Tribe girl began packing up the supplies and putting them in the tent. Zuko finished his stew, then realised he had no idea where he was.
"Where are we?" he asked.
"In a forest," the Waterbender answered, her voice muffled from inside the tent.
"I can see that," Zuko snapped, "Which forest?"
"I don't know," the Waterbender answered, exiting the tent to pick up more supplies, "Sokka and Aang read the maps."
Zuko scowled silently at her. The Waterbender picked up his empty bowl and hesitated.
"Do you want some more?" she asked, indicating the mostly full pot.
"Why am I here?" Zuko asked instead of answering.
"Aang didn't want to leave you behind," she said, "Earth Kingdom troops sometimes stop off at that herbalists. Aang thought you'd be safer with us than with them."
As much as Zuko hated to admit it, she was right. The Avatar and his friends had never tried to kill Zuko, but a group of Earth Kingdom soldiers on finding the prince of the Fire Nation would be less than merciful. The Waterbender filled up the bowl again and held it out to Zuko. He accepted it, still hungry. The girl scooped some out for herself and started eating, sitting across the campfire from Zuko.
The Water Tribe boy stumbled into the campsite, looking surprised to see it there. He smiled at his sister and immediately went to the cooking pot.
"Hey, Katara," the boy said, "What's for – ah!" he caught sight of Zuko eating, "He's awake!"
Zuko scowled at him and the girl sighed.
"Where's Aang?" she asked, handing her brother a bowl a stew.
"He saw something and wanted to go investigate," the boy answered, digging into his stew hungrily.
"Is that wise?" Zuko found himself asking.
The Water Tribe siblings both looked at him, surprised.
"He's the Avatar," the boy shrugged, "He can take care of himself."
"Last time he was on his own he was captured," Zuko reminded them sharply, his good eye narrowing to match his burnt one.
The Waterbender bit her lip, looking worriedly out between the trees. The boy continued to wolf down his dinner, unconcerned. There was another rumble of thunder, this time closer.
"Maybe I should go look for him," the Water Tribe girl said, standing up.
She needn't have bothered. A few seconds later the Avatar burst through the trees and landed next to his bison. He twirled his staff and stamped it on the ground, a grin on his face. He held a couple of scrolls in one hand.
"Look what I found, guys," the Avatar said excitedly.
He held out a poster of himself, the same one that Zuko had been shown not very long ago. The siblings reacted sensibly as far as Zuko was concerned.
"A wanted poster," the boy said, "This is bad."
"More people know I'm back now," the Avatar said, "It's hope."
"Aang," the girl tried, "You know this is going to mean we can't go to as many towns now."
"I know," said the Avatar, his face falling a bit, "I just thought it was cool. Oh!" his face brightened again and he turned to face Zuko, holding out another scroll, "I found this too."
Zuko took the scroll with a frown. Unrolling it he could see why it had caught the Avatar's attention. The Blue Spirit's "face" was plastered across it, with warnings written down the side. There was a hefty sum for any information, which Zuko couldn't hide a smirk at. Zhao was annoyed, no mistake.
"They're really quick with those," the Avatar commented.
"Zhao's got the power to do that," Zuko said with a grimace.
"So you Fire Nation aren't all on the same side?" the Water Tribe boy asked.
Zuko shot him a withering glare. Unfortunately the Firebender's headache was still there, preventing him from doing anything more. Thunder sounded again, ominously close.
"Maybe we should get inside the tent," the Waterbender suggested, "Before it starts to rain."
Too late. At her words the heavens opened. The Water Tribe siblings dove for the tent, the boy clutching at the last of his stew. The Avatar started to, then looked back at Zuko. Zuko hadn't moved. The Avatar ran over to the Firebender and pulled him into the tent. Zuko's head throbbed at the sudden movement and he clutched at it instead of protesting.
The Water Tribe siblings were mostly dry, only a small amount of dampness on their shoulders and back. However, Zuko and the Avatar were drenched. The Waterbender wrapped the Avatar in a blanket, trying to stop his shivers. Zuko simply sat with his back straight and breathed deeply, concentrating on his Firebending. A cloud of steam rose from the prince's body, leaving his clothes warm and dry.
"Wow!" said the Avatar, forgetting his chills momentarily, "Can you teach me to do that?"
"No," Zuko said shortly.
The Avatar's face fell. The Water Tribe girl muttered something to him and he nodded, a little sadly. The Water Tribe boy gave a yawn and stretched his arms above his head. At his suggestion the group settled down to sleep, the Avatar and his friends staying away from Zuko's side of the tent.
Zuko was shaken awake with a hand pressed over his mouth. On instinct he breathed out a lungful of hot air. The hand moved away and the person it belonged to had to stifle a cry of pain. Zuko's eyes adjusted to the gloom and he realised it was the Water Tribe boy crouched over him. The Avatar and the Waterbender were still asleep on the other side of the tent.
"Listen," the boy hissed, brandishing his boomerang in Zuko's face, "I'm warning you. You hurt either of them and I'll kill you." At Zuko's silent stare he continued, "They're my family, and I don't want some no-good Firebender hurting them. Clear?"
"Family," Zuko said after more silence.
"That's right," the boy whispered, "If you knew anything about that, then you'd leave them alone."
Flames shot out of Zuko's nostrils at those words. He sat up, not noticing that his head wasn't spinning this time. The Water Tribe boy moved back, but the determination was still clear on his face, even in the darkness of the tent.
"Family," Zuko repeated, snarling the word, "I'm doing what I have to do for my family. My father–" he cut himself off, taking a calming breath before continuing. "My father expects me to capture the Avatar. I'm not going to let him down."
"After everything Aang's done for you," the other boy shot back angrily, "He saved your life. Twice! And you still want to hand him over to the Fire Lord? You're pathetic."
"You don't know the first thing about me, peasant," Zuko snapped, smoke trailing from his clenched fists.
"I know you've been banished," the boy said, gaining a wary gaze from Zuko, "I know you think you need to restore your honour. I know your name is Zuko and that you were prince of the Fire Nation. You're travelling with your uncle and you hate Zhao," the boy gave a grin, "Do you even know my name?"
Zuko stared, taken aback. It was slow, but the Water Tribe boy's name finally appeared in his mind.
"Sokka," Zuko said, "Your name's Sokka. You're from the Southern Water Tribe. You are – were – the oldest man in your village," he continued, "Your sister's called Katara and she's a Waterbender, and you're not."
"Fine," the Water Tribe boy interrupted, "That's enough."
The two boys watched each other warily. The rain beat heavily down on the roof of the tent – fortunately waterproofed. The Water Tribe boy was the first to break the silence between them.
"Why are you still here?" he asked, "You haven't even tried to kidnap Aang yet."
"The medicine made me barely able to walk," Zuko snapped, "I wouldn't be able to get anywhere with the Avatar in that condition."
"So as soon as it wears off you'll go straight for Aang?" the boy asked, his grip on his boomerang tightening.
Zuko didn't bother to reply.
"He's just a kid," the Water Tribe boy said, "He doesn't deserve the sort of torture you Fire Nation types are going to inflict on him."
"He's the Avatar," Zuko said firmly, though his voice softened slightly as he added, "I'm not going to hurt him. He needs to be captured, not dead. If he dies he'll just be reborn –"
"– Into the next nation in the Avatar cycle," Sokka finished, "I know. But," he started, watching Zuko carefully, "That's not how Zhao saw it. Aang said he was going to be kept alive, but just barely."
"Zhao's cruel," Zuko said shortly.
"And the Fire Lord?" Sokka pressed.
Zuko's hand drifted up to his scar subconsciously. The Water Tribe boy noticed and grimaced. Zuko dropped his hand back to his side and scowled at the other boy.
"If the Avatar is safely locked away I doubt my father will see the need to hurt him," Zuko said.
"That's not good enough," the Water Tribe boy snapped.
Zuko was taken aback at his tone. He scowled heavily at the boy, who glared back.
"What do you expect me to do?" Zuko snarled, "He's the Fire Lord, I don't have any say against his decisions."
"Aang may have brought you along out of some misguided sense of good," Sokka said, "But the only reason I'm letting you stay right now is this: If the Fire Nation captures Aang, you're going to do whatever it takes to make sure he isn't hurt."
"If any of the Fire Nation other than me captures the Avatar," Zuko warned, "I won't have a chance to do that."
"Then you best keep doing your Blue Spirit thing," Sokka said, nodding at the mask and broadswords next to Zuko, "I want the war to end and the Fire Lord to be defeated, but if that never happens, I want Aang and Katara to be safe."
Slowly, Zuko nodded. Satisfied, the other boy moved back to his corner of the tent and curled up under a blanket to sleep. Zuko lay back down, thinking things over long after the Water Tribe boy began to snore.
The next time Zuko woke it was morning. The rain had stopped and sunlight was dappled on the walls of the tent. Water dripped heavily on the ground outside as a wet branch was caught by a gust of wind. All manner of creatures were chirping early morning greetings to one another. The Avatar's bison gave a groan, which caused the Avatar and the Waterbender to start stiring.
Zuko left the tent, pulling his broadswords over his head and holding his Blue Spirit mask tightly in one hand. His head wasn't swimming, time to try some Firebending then. The bison cracked open one eye to watch Zuko, but otherwise stayed still.
Zuko put his mask to one side and stood straight, breathing deep and evenly. He struck out, glad to see flames burst from his fist. He followed with a series of quick jabs, moving into his familiar training routine.
He was so caught up he didn't realise he had company until another, smaller, fire blast matched his own. Zuko turned to see the Avatar standing a few feet away, looking pleased with himself. The Waterbender was watching them both from a distance and judging by the snores from the tent, her brother hadn't even woken up yet.
"Look, Katara," the Avatar said, lighting a fire in the palm of his hand, "Check this out!"
The Avatar proceeded to juggle the fire, while the Waterbender looked on, impressed.
"What do you think you're doing?" Zuko snapped, storming toward the Avatar.
"Firebending..." the Avatar said, wide-eyed and worried.
"This isn't a game," Zuko snarled, "Fire is dangerous!"
The fire in the Avatar's hand increased as he frowned at Zuko. It took the Avatar by surprise and he struggled to regain his balance. The Waterbender strode forward, scowling.
"I know you don't want to teach Aang," she said, "But he's going to have to learn Firebending somehow."
"This isn't about him being the Avatar," Zuko shot back, "This is about learning Firebending properly. You need to understand and respect fire before you can use it."
The Avatar extinguished the flame in his hand, looking put out. The Water Tribe girl looked annoyed, but slightly satisfied at Zuko's answer. A yawn and a sleepy greeting drew their attention to the Water Tribe boy, who had just woken up. The boy ignored the others to dig through his bag in search of breakfast. His sister walked toward the tent.
"Right," she said bossily, "We should be moving. Sokka, help Aang load up Appa."
The Avatar cheerfully began grabbing things from the tent and securing them to his bison's saddle. The Water Tribe boy followed suit, grumbling around the bread he had stuffed into his mouth. The Waterbender frowned at the wet tent and tried to Waterbend the moisture off. Her stance was off and her movement was slightly jerky, resulting in only a small patch of the tent becoming dry. She scowled at her efforts, but tried again.
"One of my best friends used to be called Kuzon," the Avatar said brightly, "The two of us, we'd get in and out of so much trouble together. I used to visit him all the time in the Fire Nation." That caught the others' attention. The Avatar continued speaking, watching Zuko, "If we knew each other back then, do you think we could've been friends?"
There was a long moment of silence. The whole world seemed to be holding its breath to see how the banished prince would take the Avatar's offer. Zuko was tempted. The Water Tribe boy's words about family were coming back to him, he and his sister had accepted the Avatar, and the Avatar had accepted them in return. However, like he said last night, Zuko had his own family to think about.
His blast of fire was slow, giving the Avatar plenty of time to jump out of the way. The Water Tribe siblings ran for the bison, climbing onto its saddle as fast as they could. The Avatar whirled his staff, blocking the fire Zuko sent at him. The Avatar jumped onto his bison's head and gave a command. The huge creature took off, showering Zuko with water as it brushed through the damp branches above.
Zuko watched them go, stopping his attack once they were airborne. The bison and its passengers cleared the leafy canopy and vanished from sight. Zuko was left alone in the clearing with his Blue Spirit mask and a mostly wet tent. The Firebender picked up his mask then, after a small amount of hesitation, packed up the tent and hoisted it over his shoulder.
A shadow flew overhead and Zuko looked up. Something fluttered down from the sky, Zuko dropped the tent and caught it. It was the wanted poster for the Blue Spirit and attached to it was a map with an X clearly labeling where he was now. His boat was no more than a days walk away, Zuko noted with satisfaction. Picking up the tent again, Zuko set off into the woods.