One evening during their travels in the Earth Kingdom, the gang stopped by a narrow river that cut through high hills. One side of the river was flanked by a stone cliff, but on their side was a bank of black mud, where vibrant yellow reeds were growing. Aang and Katara waded into the river to practise waterbending.

Aang had improved tremendously since the Northern Water Tribe, but in sparring Katara still seemed to have the edge.

The practice would usually start with drills, with Katara going over the finer points of a stance, the feel and spirit of a certain technique, or . A nascent competitiveness between them would slowly come to the surface. There were techniques that Aang could do just as well as Katara now. So she would move them on to harder ones. If he could do these, she'd challenge him to keep the same standard under pressure. Slowly it would become a real sparring session. Then the teacherly Katara would be gone; her stance would be whip-like, each move efficient and unexpected. Suddenly Aang's form was a little too obliging; small mistakes would creep in; he'd make a minor mistake and Katara would capitalise. This time was no different; in a split second the tide had turned and Aang found himself flat on his face in the black mud.

Toph and Sokka hollered. "Another win for the Southern Water Tribe!" roared Sokka.

"Stop holding back twinkletoes!" laughed Toph. "Give us a real show next time!"

Katara scowled. This had become a favourite talking point for Sokka and Toph in the last weeks. It needled her that however much Aang insisted he hadn't fallen face first in the mud on purpose, Toph and Sokka didn't seem to believe she could really win. But if she said this it just encouraged their teasing.

"I can tell when twinkletoes is moving through his bending forms too slow. He'd never dare do that with me. Right, twinkletoes?"

Aang shrugged helplessly.

"You need to up your game Katara. The student shouldn't be able to beat the master! Right, Aang?" She gave Aang a playful shove, and he fell back into the mud.

"He didn't win," said Katara through gritted teeth. "And besides, Earth is his opposite element. It's going to take him longer to get to your level! And what would you know about waterbending forms anyway?"

Just as Katara was starting to raise her voice they heard an almighty creak of splitting wood. A few seconds later the river rippled with swashes of water from upstream.

Something circular and heavy came flowing downriver, around the shoulder of the cliff. It was a waterwheel; mostly intact, bobbing high in the water, and surrounded by a mess of broken beams and sodden thatch, it looked like the flagship of some derelict navy. Among the mess a brown shape clung to the waterwheel. As it bobbed up and down, the shape would surface, then duck under the water, dragged by the wheel's weight. The shape was a person.

Aang sprung to Katara's side in the river. With a few deft movements their waterbending parted the debris of the broken house and brought the waterwheel nearly to a stop. Aang waded closer and dragged the figure from the wheel. In the water he was light - he must have been the same age as Aang - but he clung by reflex to the spoke of the wheel. But at that moment Sokka appeared by his side. Together they pried him away and carried him to shore.

The boy was dark skinned, with tranquil features. As he lay on his back by the fire it was hard to imagine he'd just nearly drowned. His mouth was parted slightly. But as soon as Katara put her healing hands on him he spluttered, water came up from his lungs, and at the same moment his eyes opened and met first Katara's gaze, then Aang's. His eyes were startlingly blue.

When he had recovered from the shock of his awakening, the boy sank into a reverie, staring into the fire. They asked him questions but he continued to stare into the flames. Finally, by coaxing and encouraging he started to speak in a hoarse whisper. He glanced up briefly and caught Katara's eyes for a moment. She sat by his side and leaned closer and closer until she could just hear him speak. Her ear was almost by his lips.

He told them his name was Dawa. He'd lived in the millhouse up here with his father, grinding grain for the villages further up in the hills. His mother had left when he was small; some in town thought she'd gone to join the war. Then, a few months ago, he had woken up to find his father gone too.

"I didn't know what to do," said Dawa miserably, "so I stayed up here and tried to keep the mill going myself. Until he gets back. But there was too much work to do, and I couldn't work the mill by myself…" he started to sob.

After more consoling, Dawa began to find his voice. They asked him if there was anyone who could take care of him where his Dad would think to look when he got back, and he finally mentioned that his aunt lived at the foot of the hills, where the river flowed into Lake Mi-Ling. This was the sacred lake of Dawa's people, he explained, whose ancestors had lived by the lake's banks for generations, and the town was his hometown. They knew it as the Mirror Lake, for its clear waters, and the legend that it reflected deep truths back on those who stared into it.

It was a day's fly away.

"You know guys, we really can't afford any more detours…"

As the gang swivelled to stare him down, Sokka threw up his hands.

"Nevermind!"

That night Aang was woken by the sound of soft footsteps. Rolling over, he saw the silhouette of Dawa standing motionless by the riverside, swaying slightly. The moon was nearly full, the reeds casting silver shadows along the bank.

Aang rose and approached him cautiously. As he got closer he could see that Dawa's eyes stared vacantly ahead. Aang said his name, softly first then a little louder, but he didn't reply. Then he reached out and touched his arm.

Dawa jumped and blinked.

"Are you ok?" Aang asked.

Dawa rubbed his eyes. "I was sleepwalking," he said. "And I had a strange dream."

He looked at Aang curiously for a few seconds, his striking eyes glimmering in the moonlight. He knelt down and splashed a little water on his face.

"Do you like Katara, Aang?" He said suddenly.

Blood rushed to Aang's cheeks, but before he could reply Dawa asked, "Do you love her, Aang? You do. Don't you? Have you said anything yet?"

Now Aang felt cold. "How did you know… I mean, what makes you say…"

"I saw straight away. It seems so strange, doesn't it? How long did you say you've travelled together? But there's still this gulf between you…"

"Don't tell Katara, alright?" Aang stammered

Dawa was smiling slightly, a corner-of-the-lip smile that made him look older. "Why not?"

"Because… I want to tell her myself!"

"Fine. I won't." Dawa continued to return Aang's gaze until Aang turned away. "But someone should say something."

The next day they took off early on Appa. The rocky cliffs soon receded as they followed the course of the river into green, wide valley country. Once or twice, they noted black clouds of thick smoke on the horizon - a sure sign of Fire Nation incursions. Raiding parties, Sokka suggested solemnly. He and Katara knew about these kind of attacks all too well. It seemed extra important to get Dawa to the relative safety of the town soon.

Despite this, after a night's sleep Dawa was in high spirits, and easy company. He laughed boyishly as he pushed them to talk about their adventures. Aang, riding on Appa's head, often heard the gang laughing at something Dawa said. He couldn't help but crane his head over his shoulder now and again, keen to join in; and, he had to admit, to see if Katara laughed more than Toph and Sokka. Occasionally the conversation from the night before came back to him. It seemed surreal now, dreamlike.

Then Appa let out a moan, and Aang noticed they were losing height.

"What's up buddy?" Aang lamented. "You seemed fine this morning! What's happened?"

"Maybe he ate the reeds," ventured Dawa. "The reeds around my house have poisonous stalks."

They came to ground soon after, and Appa lay down, curled as far into a fetal position as his enormous frame would allow. His groaning certainly suggested a stomach upset.

Aang was set against leaving Appa, but Dawa explained that the reeds had never been known to be fatal to a person, let alone a 1-ton sky beast, so there was nothing to fear. They were about a day's walk from his hometown, given the distance they'd covered on Appa already.

He looked vulnerable as he explained this, with his palms held out imploringly, and there was a note of desperation in his voice.

"I can look after Appa for a day or two. You guys go ahead," said Sokka. There were nods of approval.

Aang was about to ask if the three of them really needed to go together, leaving Sokka alone. But something funny had happened, and it had happened in a second.

The march was setting off. Dawa had looked at each of them - Katara, Toph, finally him - in turn. His expression was imploring. Irresistible. Sometimes these instant social decisions - who walked with whom, who stayed and who went, who was told and who was excluded - that seemed so random to an outsider, felt so purposeful to someone on the inside. Yes, Aang thought, Dawa must have done something - what was it?

Aang set off to join the three of them who were already a few paces ahead, Dawa chattering away between them. Dawa's voice was loud, his arms thrown out in gesture. He looked like a kid who'd got the adults to let him have his way.

The very same thing happened, at least as far as Aang could see, later that day. They'd stopped for a bite to eat, and as they were following the river Katara and Aang again took to waterbending. Aang immediately felt his spirits lift. When he sparred with Katara all the fears he kept in his heart seemed to melt. He was absorbed. They knew each other's moves, habits, techniques so intimately. It was a dance.

Jaw set, eyes drawn into a scowl. She spun through her technique, her soaked ponytail whipping against her collarbone -

And Aang realised his feet were hurtling up and his head plunged temple first into the water.

He'd lost again. Oh well! Rather than surface straight away he allowed himself to slowly float the few feet to the surface, looking up through the water's refractive lens into the blue sky. A darker shadow moved over him, and Katara's hand took hand tightened as she helped him up.

Squinting against the water in his eyes, Aang thought he saw a self-satisfied smile on her face. Then he heard a little gasp of surprise from the riverbank.

Dawa's mouth was agape. "I don't believe it!" He cried, "did the Avatar just lose?"

Aang's face fell as Toph howled with laughter. "He's on to you, Aang!" But Aang hardly noticed this, because Katara too had chuckled. A lump welled in his throat as he thought back to her reaction to this very same taunt the evening before.

"Aang's doing a great job," said Katara to Dawa.

"You make it look so easy," said Dawa, "so natural." He hesitated. "You know, it's said that the people of Mi Ling lake were once waterbenders. It's said that the lake gives us this power."

Katara tipped her head sagely. "Nothing external can 'give' or 'take' bending, Dawa. Bending comes from within you. It's a form of self-expression."

Dawa frowned. He looked into Aang's eyes, over Katara' shoulders, as he considered this. Then he broke into a shy smile. "I would love to try it, Katara. Will you give me a lesson? I'd be honoured."

As though by magic they were almost by the bank. As the conversation had been going on, they'd been taking small steps towards each other. Now it was just a single step, and just like that Dawa planted himself between Aang and Katara. A jolt swept up Aang's arms, not unlike the feeling before he was attacked. But Katara smiled, at ease. Her hands were already coming up as though in an embrace, starting the gestures of a basic waterbending move.

Aang slumped down on the bank in a daze. Somehow it had seemed perfectly natural that he should be interrupting the Avatar's lesson, and standing in his exact spot taking pointers from Katara.

Dawa took ungainly stance, biting his tongue in concentration. Katara's hands shadowed his. With a painfully slow movement Dawa opened his stance. At first, nothing. Dawa kept trying, under Katara's watchful assistance, all the while glaring into the water. On the tenth or eleventh try, a thin chord of water blipped up from the river and hung like a necklace between his hands..

Katara cheered.

"You're not jealous, are you twinkletoes?"

Aang jumped. He must have been deep in thought for Toph to sneak up on him. The question sunk in and a warm blush ran up his cheeks.

"Why would I be jealous?"

"Because he stole your teacher, obviously."

"I guess so,"

Katara was leaning over what was now a ball of water suspended between Dawa's hands. She was smiling.

Aang hugged his knees tighter. At least it seemed that Dawa hadn't said anything to her. Anything about their conversation that first night… a few times that day he'd almost started to drift towards the subject; or he'd lingered on a jumping-off point in the conversation just a little too long, for example when they mentioned the cave of two lovers. As though taunting him, Aang thought.

"Well, he is kinda cute," said Toph.

Aang almost jumped out of his skin. "Cute?"

"His voice is cute anyway."

"Toph, you can't say stuff like that," said Aang furiously. "You never say stuff like that. And you didn't even punch me and do that 'never speak of this' look. What's going on with everyone today?"

Toph punched him.

The lesson had just finished, but they were taking their time before setting off again. Walking for so many hours was tough on the legs, especially for travellers accustomed to being flown around, so they all put off the moment they'd have to start walking again.

In a few seconds a strange thing had happened. Aang was still sitting where he'd flopped down before. Toph was lying a few paces up on her side, resting her legs. Dawa was next, then Katara. In that moment Katara turned away, looking downriver at something.

Dawa looked over Toph's head at Aang and grinned. Then he swung his arm in a circular motion, and a sheet of water sluiced from the river and followed his hand in a paper-thin sheet. The sheet was as clear as a mirror, as silent and ephemeral as the reflection on a lake. Aang stared.

Dawa swung his hand and the skyscape of crystalline water advanced noiselessly, spreading and thinning - until it collapsed into a torrent over Toph!

"Kata-RA!" Toph screamed, leaping to her feet. Katara swung round in surprise, just as a slather of mud and riverbank fell over her in a wave.

Standing between them, right in the conflict zone, Dawa was struggle to hold in a chuckle.

Once the fight had finally died down, and Katara and Toph had dried and cleaned themselves up, Aang tried to explain, again, that it was Dawa. But Katara only looked at him pityingly. "Dawa can barely waterbend, Aang.

"I would have heard him waterbend," said Toph, through gritted teeth.

"What about me?" said Aang hopefully. "Maybe I did it as a prank? As a joke?"

"Don't be silly, Aang." said Katara.

But if I didn't start it, Aang thought, who does she think did?

That evening they crested a steep peak, and looked down on Mi Ling lake. Shimmering in the setting sun among steep, ridged hills, it was like wine in a chalice. As the sun moved below the far hills, its waters were turning from red to silver.

A cluster of low brown buildings on the far side was Dawa's hometown. If they hurried, they could be there the same night. But at that moment, Katara froze, one hand around her throat.

Her mother's necklace was missing.

The group retraced their steps down the hill, but the necklace was nowhere to be found. Katara thought it must have come off in their 'little fight' - she said, glaring at Toph.

"Don't accuse me", said Toph indignantly, "and besides, I would know if it had fallen. I can see through the earth, remember?"

"If it's not there, where is it then, Toph?"

Aang hastily stepped in to stop the 'little fight' blossoming again. Dawa looked on in amusement. He was wearing a lopsided, why-is-this-a-big-deal grin.

They agreed to retrace their steps the next day, back to where they'd left Sokka and the sick Appa. There was nothing else to try. Then they noticed Dawa again and Aang sighed. First, he said, they'd have to walk Dawa to his village.

"If that's not too much trouble," said Dawa, holding his hands up. "I mean, if the necklace is more important…"

Katara looked hurt. She'd obviously thought she'd made a connection with Dawa, Aang thought, and now he was mocking her most treasured possession.

Scowling, Aang set about preparing camp.

Rather than help, Dawa unexpectedly skulked off after these words, back to the crest of the hill. He left a bitter taste between the three of them: Toph sulky and withdrawn, Katara worried and confused. Aang looked at them helplessly.

Something unexplainable had entered the group along with Dawa. Something wasn't right.

When the tents were up, he reluctantly walked the few paces to the top of the hill, where a light wind was blowing. Dawa was standing leaning into the wind, looking out to his village. He turned when Aang approached. The sun had set, but a bright moon lit up his blue eyes.

"You fight a lot," said Dawa expressionlessly.

Aang bristled. "Not this much usually."

"Maybe it's the lake. It's said that it raises troubles to the surface."

When he wasn't talking, Dawa stared back out to the view, to the town and the lake, as though drawn to it. But when he glanced at Aang out of the corner of his eye his eyes were shrewd. Nothing like the eyes of a 12-year-old.

And Aang noticed with a start that they were not even blue, but silver-blue; and the silver seemed almost to roll around his irises like mist.

"If you want to head straight back, I won't be offended," said Dawa. "You've done more than you ever had to already."

Aang took a deep breath. "It's ok, Dawa. Fire Nation patrols could be nearby. Not far to go now."