Takes place in the canon universe. Sokka's POV. Enjoy:)
He distantly perceived that the late afternoon sun was making its way into the room through floor long windows behind the couch Sokka was sitting on. Sokka smelled old parchment and book binders mixed with that of fresh book print. Candles were being lighted around him, the peculiar scent of wax beginning to reach his nose as well. Tall, wooden book shelves surrounded him, giving Sokka a strange feeling of comfort.
He shifted in his seat, continuing his escapade into the world of Fire Nation technology, or Fire Nation vessels to be precise. Sokka turned a page, skimming a sketch of a ship's main engine. He frowned, not quite getting the cycle that was pictured, deciding to continue reading after some more fruitless wondering. Maybe it would be explained later.
Whatever Sokka might have told the others, getting information on the Fire Nation to help win the war was only one of the reasons he had decided to sneak off to the Ba Sing Se City Library. Sokka had to admit that he had been generally interested in the enemy's tech ever since scheming with Teo's dad at the Northern Air Temple.
And since Ba Sing Se was a huge city, they had to have a library that was equally large. And "there is no war in Ba Sing Se" aside, they had to have at least something on the topic.
Sokka regretted not having checked Wan Shi Tong's place for that kind of information (because he was sure he would have found floors on it) but he didn't exactly have the time to skim a few more books when the owl spirit had decided they were to longer welcome in his library.
So here he was, working with what he had (as he always did).
And, luckily, he had found something that didn't look like it was a hundred years old (see: Hahn's up to date uniform). Which he was busying himself with at the moment to make up for the time he had spent searching.
As he turned another page, Sokka couldn't help a grunt of surprise (yes, a grunt of surprise. No, his voice did not crack) as the booklet seemingly ended in the middle of a sentence.
Putting it down, he tried rising to his feet to search the secluded section where Sokka had found it among half rotten scrolls and spider webs, only to give a yelp, sitting down again.
He had risen too fast, causing a wave of cold to wash over him and black to creep in at the edges of his vision.
"Knocking yourself out won't do it, peasant."
A different sort of cold seemed to creep all the way into his bones at the sound of the familiar voice, cold sweat starting to form on his spine from the dread Sokka felt.
Snapping his head to the figure leaning against a nearby book shelve, his worst fears were confirmed.
He looked thinner than when Sokka had last seen him, raven looks falling way over his eyes. Yet not enough so to hide the burn mark that should forever haunt Sokka's dreams as a sign of defeat.
Of failure.
Golden eyes, Fire Nation eyes, were glinting at Sokka in the semi darkness, sunset lighting good enough to show Zuko's crossed arms.
Swallowing his horror and racing thoughts (Should he jump out of the window behind him? He was on the first floor so that would work. He could warn his friends-), he spoke up.
"Seems someone made it out of the desert alive. What a shame."
Sokka promptly decided that provoking the jerk hadn't been a very intelligent plan of action, but could you blame him for being frightened of the guy who had chased them halfway around the world?
Sokka was already mentally apologizing to all the beautiful books on architecture and history around him that were sure to be destroyed in a matter of seconds, but the explosion never happened.
Sokka blinked. Zuko raised an eyebrow, probably following Sokka's train of thoughts (damn him!).
He took a step closer and Sokka, in his panicked state, mind you, sprang to his feet…
Only to almost faint again.
"For the love of-idiot, sit down!"
Sokka felt two firm, warm hands force him to a seat.
"You don't get to tell me what to-"
Zuko ignored him. How dare he?!
"If you wanna get up so bad, do it slowly."
He gave Sokka an expectant look.
Sighing, Sokka complied, rising as though he was in a trance. Knees slowly coming out of the ninety degree angle, until Sokka had assumed a secure standing position.
"I know how to do this sort of thing.", Sokka grumbled.
Zuko actually chuckled.
Sokka narrowed his eyes. "What are you doing in a library, anyway? Stalking me? Trying to ambush me so I will get you to Aang?" Zuko either ignored or missed the animosity in Sokka's voice when he replied:
"Architecture. Never been to Ba Sing Se before. They have, uh, a style that's different from the-the other Earth Kingdom buildings, you know, Omashu, Kyoshi,…"
Wow, Sokka had never seen the prince ramble. Like, really ramble. Scratching his head and looking away and all. Something in his attitude made Sokka less suspicious of him, whatever that was.
Still, he decided to dig a bit deeper. Just to confirm the jerk wasn't lying.
"So, how are Earth Kingdom and Fire Nation architecture different? You know, apart from the colours, obviously.", Sokka asked, feigning interest.
To his utter amazement, Zuko proceeded to give him a lengthy speech about all the differences. Really all of them, from the main building elements to the positioning and shape of the doors and windows, with something akin to passion in his eyes.
He tripped over his words in his excitement, barely coming short of jumping up and down while he talked.
So the Fire Prince who was keen on delivering Aang to the Fire Nation had a soft spot for exterior house design. Interesting.
After a while, Zuko interrupted himself.
"S-sorry" He laughed self-consciously. "I'm probably boring you to death with this.".
Shocked at how awkward Zuko could actually be, no, was in reality, Sokka sputtered a bit himself.
"What? Uh, no. I'm just-surprised. I would never have expected you to be so-well." He made some gestures that were supposed to express what he was trying to say.
Zuko gave him a curious look, crossing his arms. "So...what?"
"So...normal."
Something shifted in Zuko's expression, before he decided to brush off the topic entirely.
"So, what...were you reading?", He asked as though this was a totally normal question coming from him.
Sokka glanced at the offending booklet with mixed feelings. Should he lie? But since nothing else came to his uncooperative mind, Sokka sighed, deciding to stick with the truth.
"Fire Nation vessel engines. I like technology."
Zuko looked skeptical at this declaration, which he kind of had every right to. It probably seemed a bit too convenient that Sokka would be interested in Fire Nation war tech and be happening to try winning a war against said nation. Even though it was true.
"What? We don't exactly specialize in tech production in the South Pole."
Zuko nodded, though the tightness in his jaw showed he still wasn't entirely convinced.
Sokka decided to ignore that as an idea formed in his mind. He turned to the page with the sketch, holding it up for Zuko to examine. Fire Nation or not, it would still be interesting to find out how this thing worked.
He explained to Zuko where he was stuck, earning himself an interested look only slightly clouded with suspicion.
Zuko gave Sokka a long, pestering look. Sokka stared right back, unwavering.
Nodding, Zuko seemed to decide he could elaborate. It was quite the info-dump, but Sokka could follow him more or less as he explained the processes inside the engine, how heating cycles made the water transform to steam, other mechanisms accelerated the gaseous water to generate energy, what all the components of the systems were called, how the cycles could be regulated, etc.
When he thought he had got it, Sokka gaped at the concept drawing and Zuko in turn.
"This-this is...brilliant! I mean, it's got to be great to run something like this. Every day! Such an upgrade to some dumb bison!"
Zuko gave him an exaggerated eye-roll.
"I was blind with fascination every time I passed my coal shoveling crew."
Sokka punched him. Though without the intention of hurting him.
"Shut it, column boy!"
"Okay, okay.", he replied, blushing slightly and raising his arms in a defensive gesture.
Zuko let him leave the library when Sokka decided to return to the villa Team Avatar was currently occupying.