Disclaimer: I don't own D. Gray-Man or Harry Potter.

Beta-read by espeon16

Group Dynamics

Lavi slumped over Fifty-One Ways to Find a Needle in a Haystack and stared at Allen until the latter met his gaze.

"What?" A pale eyebrow was raised.

"M'bored." He was fully aware of his inner hypocrite coming out here, and so was utterly unsurprised when Allen reacted with a sigh and turned back to his own book. It had been Lavi's idea to commit a day to library research (both for the mission and, secretly, the problems in his own head), but still. There was nothing in the contract – the figurative one formed after the shameless pleading, bribery, and coercion from Lavi – that said Lavi couldn't whine about his own misjudgements.

Besides, there was no progress being made whatsoever. Most of the volumes here Lavi had already read, but he had the other two skim them over again, just in case he'd missed anything in his headache-induced haze. He was getting rusty with his memorization. Bookman wouldn't be pleased.

Really, his mentor wouldn't be pleased with the majority of the things going on in Lavi's head at the moment. Lavi certainly wasn't. He turned to Kanda and prodded at the other exorcist's head.

"Hey." His target was either ignoring him or very, very interested in the contents of his book. Lavi glanced at the cover. Five Hundred Household Spells and Their Origins. Hm. Hard to tell. "Hey, Yuu-chan."

His response was a deep, deep sigh, somewhat muffled by the book. "What."

"What time is it?" Kanda's right arm twitched a little, as if he was holding back the urge to punch a rabbit.

"The clock. Is right. Behind you." Gritted teeth and growling didn't make for clear communication, but Lavi spoke "Yuu-chan" well enough to hear the undertone: 'also – leave me alone or I will forcibly separate your head from your body'. Or something similar; Kanda wasn't the unpredictable type.

Lavi debated whether or not he should let the conversation die there. On one hand, Kanda was already irritated beyond healthy levels, and there actually wasn't much stopping him from killing the junior Bookman, just a little bit. On the other hand, though, there were all the things that Lavi needed distraction from: the raging headache; the lack of progress on anything; the nervous energy hanging in the air, generated and passed around and added to by the other students in the library.

At one point, Hermione (with Harry and Ron in tow) had popped in to check in on them, as they were wont to do. After finding no evidence of trouble (either caused by or attracted to the exorcists), they'd settled at a nearby table and tried not to look like they were still watching the table of transfers. The furtive glances and hushed whispers really weren't helping the situation.

Kanda was saved from being subjected to further prodding and testing of his temper by the almost-familiar movement that had caught Lavi's eye. It was a different kind of recognition, though, because it was from this persona, this life. It was worrying, for the same reason, and it consisted of a series of small things: one's grin was a little too sharp, the other's eye-roll in response; the loping, casual way they walked, like they had a clear purpose and they were sure they couldn't be stopped; the way they moved together, like siblings, though they couldn't possibly have been family. Their appearances were as mismatched as leftover socks.

Speaking of appearances – Lavi frowned and looked closer. The taller one had the air of sports-player confidence in the way he was dressed, but he slouched and his thumbs kept trying to find pockets that weren't there. The other had the studious look, but he bounced as much as he could get away with in a library and seemed to keep forgetting that he had glasses on.

In short, they looked like strangers in their skins, and one shrill giggle set Lavi's hair on end.

"Kanda." The swordsman's head snapped up, aware of the seriousness from the one word. Lavi frowned and shot one last uncertain glance at the strange pair, hissing, "I think there are Noah here."

"What?" Hermione was turned around and facing Lavi in a second; Allen's hand instinctively started creeping towards his cursed eye; Harry and Ron were scanning the room, shoulders tense and eyes wide – though they hardly even knew what they were looking for. Kanda glared Lavi down for an explanation, but he already had a hand on Mugen. Lavi would never be untruthful about something like this – and him being mistaken was even less likely than that.

"Where," was his question, and the redhead nodded at the others, waiting for the rest of their gazes to settle on him.

"The two over there. They don't look like Noah, somehow, but they look like they don't fit, and they move like the twins." Kanda couldn't quite see it (and, judging by the expressions, the others couldn't either), but there was something to be said about the fact that they'd worked in teams since Lavi joined the Black Order.

"I'm on it." Kanda made to stand up.

As Lavi explained, Hermione watched the alarm slide off of the others and give way to confusion. Even the other exorcists looked puzzled. She could spot a hint of doubt in everyone, and that was enough for her to take action.

"Wait. Do these Noah often take elaborate disguises?"

Lavi furrowed his brow, impatience clear in his posture. He seemed to be wondering why she was asking such a strange question, when it was obvious (to him) that it was an urgent situation. "No, but that doesn't mean they won't. Wasn't there a Polyjuice Potion or something to –"

"How would they get their hands on Polyjuice Potion?" Ron interrupted, not unkindly – he seemed legitimately lost, but Lavi was getting more and more agitated.

"It doesn't matter, we need to get to them before they…" Lavi continued, but Hermione stopped listening and scrutinized him a little more closely. He had been under stress for a while, and he hadn't seemed quite stable in the first place. It was possible that the students were Noah, and Hermione knew that she was supposed to trust the exorcists, but – she couldn't just do so blindly. The exorcists were human, too, and people made mistakes, and none of Lavi's points were more solid than a guess based on a flicker of movement.

Kanda was starting to move. If Lavi was wrong – and it was likely, in this case – the consequences would be horrible for any and all parties involved. Kanda was already under suspicion, and if those turned out to be students on the sharp end of his sword –

Hermione reached for her wand. "Wait. Don't move yet."

Allen knew Lavi was coming across as a bit hysterical, paranoid, frantic, desperate. His logic was heavily dependent on loose bits of tiny, tiny things, and the situation he was implying seemed absurd. Noah, with access to advanced potions, and not attacking? What would they want from a library?

But Allen also knew that Lavi didn't lie. Lavi didn't overreact, not if it put the mission at risk (and it would, if they got in trouble with the Ministry), and Lavi was almost always right.

He may not have been as eager as Kanda to blindly charge into battle, but by the time that everyone made to move and then froze, he was ready to believe what Lavi was saying.

"They're getting away –" Allen slipped off his glove.

Kanda, of course, was not inclined to follow orders from a witch girl. Hermione, of course, had a wand and was good at using it. Harry, of course, would see the logic – of his friend's side; Ron would follow their lead. And Allen knew that there wasn't time to argue.

Lavi was the only one still seated when the library erupted into chaos.

"You can't go! You'll get into trouble – the Ministry – argh!"

"Damn it, you don't understand, they're dangerous –"

"Don't move. Everyone stop right where they are –"

"Guys! They're getting away!"

"Why would they even be here, is the question –"

"There's no time for this!"

All the younger years, jumpy and alert, had their eyes on that table from the start, and especially so when Kanda had hinted at moving. By the time Hermione was up as well, curious older years and some wary staff were watching. And, following that, as soon as there was any hint of conflict, the rest of the room set to motion, milling around and amplifying the general confusion.

Hermione had her wand trained on Kanda – having deemed him the most dangerous – but her attention on Lavi – having decided he was most clever. Harry was on crowd control and possible-Noah watch and was also trying to back up Hermione's point, and it just about stretched his multitasking skills to the limit. Ron and Allen were trading exasperation and frustration through shouting and elaborate gesturing.

This set-up did not help to minimize the pandemonium when the exorcists started moving.

Lavi had but a quarter of his mind devoted to the escaping Noah, another quarter for team dynamics, and the rest to the headache wreaking havoc on his concentration. His weapon was in his hand, somehow, and the Polyjuice Potion – if that was what it was –seemed to be wearing off. It didn't matter at this point; everyone else was too engaged in the unfolding scuffle to notice a few gray-skinned strangers slipping towards the door. Lavi attempted a subtle slip-out through a gap in the crowd to follow.

However, there was something to be said about Hermione's attention, and she swiftly whipped in his direction what might have been a Petrificus Totalus or an Arresto Momentum or even an Avada Kedavra, as far as Lavi could remember afterwards. There was too much noise and too much movement and too many people, and he was battle-ready on adrenaline but the enemy was getting away.

Thankfully, a third-year was jostled into Hermione and messed up her aim; the spell went wild and flickered out harmlessly on the ceiling. Unfortunately, this constant shoving in the crowd closed off the gap providing Lavi a view of the Noah before he could react to the opportunity and move.

Kanda, meanwhile, was freed from the wand pinning him by this distraction, and had no qualms about knocking over a few students on his way to the enemy. Also, as said enemy's disguises were shed, it was fully assumed that he'd be free to attack now.

Sadly, that was not the case. While most were busy shying away from his unsheathed sword, a few brave (stupid?) older students took it upon themselves to stand in his way, wands up.

Kanda had had it with the wands. He was on the verge of stabbing them all (stabbing, but not killing, because otherwise he'd never hear the end of it) so they would just get out of his way when a hand from behind took firm hold of and held him back by his hair. He was suddenly very happy to introduce the tip of Mugen to the intricacies of Allen's inner organs. Hello, don't think we've met, mind if I just – my, what a lovely shade of red you've got there, do you always bleed this colour?

Regrettably, he had learned quite a while back that cutting into teammates, even just a little, was Not Acceptable Behavior and also, more importantly, didn't do jack for the progress of the mission. So he settled with his best snarl-glare combination and a hackles-raised "What?"

"Kanda, you are not going stab-happy on the students. I'm stressed, too, okay, but somehow I don't think getting the wizards more angry or upset is going to be very helpful when the Noah are right there."

Kanda hated it when the moyashi had a point.

"Fine, then, let me go and I'll cut up the right people, all right?" The back of his head was getting uncomfortable.

"Whoa, hey, wait a second – nobody's cutting anybody up!" Harry chose this moment to focus his multitasking efforts towards the bickering exorcists, and Kanda had to fight down the urge to go 'stab-happy' again. Meddling, however well-intended, was not appreciated right now.

While the Boy Who Lived engaged the other two exorcists on a long spiel of reasons as to why one should think and consider consequences before acting (funny coming from him), Lavi spotted another opportunity to escape the swelling, shifting mob of differing opinions. He didn't bother to check if anyone was watching him – either they were or they weren't, and there was no time to spare here. The Noah – he was certain they were Jasdero and Devit now – had struggled their way to the outer reaches of the crowd, where it thinned and allowed a clear path through to the door. They appeared to have what they wanted, and a speedy retreat was working out very well for them.

As Lavi shouldered and elbowed his way past countless bodies and indignant yelps, he kept a close eye on the Noah's movements. Jasdero caught his eye and grinned, the threads making the effect rather disturbing. Lavi grinned right back, borrowing Allen's shark-effect and augmenting it with a too-hard look in his eye that didn't match.

Miraculously, Lavi managed to get within two arm-lengths without any spells being fired at him from behind, and things were almost looking up until Devit called out to him.

"Of course you're here, Bookman." Before Lavi could process what he meant by that, he continued. "Road told us to pass something on for her if we saw you – 'He was right, he should have known'!"

His twin giggled. "He was right, he was!"

Lavi felt the pull of a memory threatening to overtake his consciousness, and then he was angry. He was angry at the Noah for knowing exactly what to say to make him pause-hesitate-pass out, and he was angry with himself for being weak enough for it to work, and he was angry at the headache and the situation and the past few weeks, and it was maybe actually enough to ward off the oncoming collapse. Apparently. Huh. Temporarily, at least, and that was all that he needed. Maybe if he managed to convince Road that it didn't work, she would stop trying. Maybe if he convinced himself, he would stop having to worry.

The world started moving again around him – had it stopped? – and Lavi moved with it, almost without thinking. His hammer was in his hand and he was swinging it around towards the twins, letting it grow to an appropriate size – before he could think things through. By the time his brain caught up, it was too late to not carry through with the movement, even though it was a library and there were too many people around. His attack left a sizable dent in the flooring, where Jasdero had been standing a moment before.

"Loading –" The Noah were shoulder-to-shoulder now, and both guns were pointed at Lavi. "Blue Bomb!"

There was no room to dodge, and even if he did, he would have been held accountable for the several students behind him who would be frozen as a result. Ozuchi Kozuchi was too far out – and too embedded into the floor – to block, so the only option was to counter.

Why were his all attacks so widely-ranged and indiscriminately destructive? He had none of Kanda's precision or Allen's flexibility. All he could do was burn, crush, destroy.

"Fire Stamp!" It took care of the ice bullet and scorched the nearby bookshelves to a crisp, but he'd missed his targets.

"Ooh, looks like our exorcist is getting angry! You know what they say – fight fire with fire!"

"Fire, hee!"

Twin pistols and twin smiles were leveled at Lavi and the combined fireball hurtled towards him. The Noah held none of Lavi's qualms about damaging property (or books). With some difficulty – the space was too tight to maneuver in properly – Lavi twisted his hammer around to block the attack, and sent another Fire Stamp in their direction. Where were Allen and Kanda? Lavi couldn't take down two Noah without backup, especially not in an enclosed space and surrounded by wizardly bystanders. Why weren't the students being cleared out?

A quick glance back provided the answer – the wizards had finally realized the legitimacy of the danger, and Hermione, Harry, and Ron had released the other two exorcists. The downside to this turn of events was that the crowd of students – why were there so many in the library, of all places? – hadn't become any more organized in the time that had passed, and the appearance of a new threat hadn't helped matters at all. It was impossible to get through without injuring someone. Hermione was biting her lip and trying to clear a path, but she appeared to be having minimal success.

"Blue Bomb!" Lavi spun back around just in time to see another blast of ice headed straight for him. He gritted his teeth and lifted his hammer with renewed determination – if he could just keep Jasdevi here long enough for Kanda and Allen to arrive –

His counterstrike deflected the attack to the side, nearly demolishing the librarian's desk. Lavi winced at the damage; at least he hadn't been the one hit by that. He squinted, trying to see through the resulting smoke-steam. To Lavi's surprise (and alarm and dismay), the Noah had opted against taking him down with an easy shot and instead had aimed for a diversion, and were already halfway out the door.

Devit twirled around to face him for a parting remark. "Sorry, Bookman, we'd really love to stay, but this is a retrieval mission, isn't it?"

"It is, it is!" Jasdero giggled and turned on his heels to bounce after his brother.

By the time Allen had arrived at the other side of the library – he hadn't realized how large the distance was from one side to the other until it had been filled with panicking black robes – the only thing left to do was damage control. There was ice coating a good quarter of the room, fire smoldering in another quarter, and upset students in the rest.

"I'm so sorry," a distraught Hermione near-wailed at Allen. "I was trying to think of a million things at once, and I just – "

"You should be." Kanda cut her off roughly, and Allen shot him a look of intense disapproval.

"No, you shouldn't. You were trying to help, and we didn't really even explain properly, and if everything had just been sorted out beforehand, all this –" he waved a hand vaguely, either indicating the tension between the two groups or the mass destruction that had resulted from it – "wouldn't have. You know. Turned out the way it did?"

He'd lost track of who he was trying to persuade – exorcists or wizards – and he wondered if it wasn't both. Before he could continue his attempts to reassure Hermione that it wasn't all her fault – and to figure out why Harry was looking at him strangely – Madam Pince, the librarian, came storming over.

"What did you do to my library?!" Allen blinked at her, deer-in-headlights mode engaged. "There are entire sections of priceless books destroyed, boy. Destroyed! Ravaged, ruined, disintegrated!" She looked angry enough to hex him, and the only reason Allen-the-actual-beansprout didn't make an appearance was the happy coincidence of Lavi wandering by.

"You!" She turned on him, disapproving distress evident in every line on her face. "Don't think I didn't notice you, with that blasted hammer, turning my books into cinders!" (Allen gathered, from Lavi's expression, that he rather thought she was using too many exclamation marks.)

"Do you even know how irreplaceable, rare –"

"Come, now, Madam. This doesn't become you." Lavi had on a cheerful, roguish grin, and took the librarian by the hand. "I'm almost certain a Reparo would fix most of this mess, wouldn't it? Certainly a witch of your caliber could manage to rectify this little mess?"

She seemed a little mollified by his flattery, and a little bewildered by his attitude, and between the two Lavi had managed to calm her down somewhat. He chattered on about specific books in sections, clearly putting his memory to good use, and a little while later – by some miracle – he had her looking mildly impressed.

Satisfied that any books unable to be Reparo-ed could at least have the contents reproduced, Allen turned his attention back to helping sort out the rest of the mess. He supposed it could have been worse – at least no one had gotten hurt. The only reason for that, though, worried him. The Noah had gone to (presumably) a good amount of trouble to get into Hogwarts and to infiltrate the library, but they hadn't even gone after the exorcists.

What were they after, if not the exorcists' lives?

A/N: Thank you for waiting! And apologies for the wait. The excuse for November was NaNoWriMo, and December's was Christmas, but the rest I was just being lazy because I'd lost momentum. And then I had less momentum because I wasn't working on it. So.

But! I promise to work on the next one right away, after this one is posted. Pinky swear.

(The reviews were what got me back on track, so thanks to all of you for the support!)

Yua-hime: Thank you so much for the lengthy review, and so sorry it took so long to get back to you. I love Lavi to bits. I think it shows up as –Man sometimes because fanfictiondotnet swallows links, and if you don't put a space after the D. in D. Gray-Man, the first part doesn't show up. I think. I'm not sure about that. I'm glad you like my adventure-y bits; I tried my best to make them interesting. I hope you're still reading this, by the way. I know it's been a while since the last update. I'd love it if you would review more, thank you!

Ennael: Here are the Noah! I hope I did them justice. It's not Tyki, but it's not Road either? My health is fine, thank you for worrying. I didn't mean it like that – I'm mostly just procrastinating. But sometimes I can get a little busy, so. I did make you wait, though, didn't I? Sorry.

Anonymous Reader: Here you go! I hope you weren't eagerly waiting the entire time, though. That would have been tiring.

Lavi-chan: Thank you very, very much for the compliments! I'm continuing it right now.

Lavi: Thank you for the review, and here's the update. Just for you. :D