Brief warning: Lots of pseudoscience, but based on real concepts. If you don't understand, look up tesseracts (actual tesseracts, not Marvel universe). Madeleine L'engle's A Wrinkle In Time might also help. If you still don't get it and want to, PM me, I will try to find time to explain (might take a week or two).

Chapter 38

"So, I still have that Charms assignment to do… study session, anyone?" Al asked as he, Jack, and the Doctor were walking back to the castle from. Ash shadowed them, just close enough to hear their conversation, but far enough away that no one could accuse him of associating with two Gryffindors (well… specifically the Gryffindor whose sister was not a Slytherin prefect).

"Really, Al?" Jack stared at the boy. "It's massive, and it's due tomorrow! I thought you said you were done with procrastinating!" Al shrugged. Ash, several feet behind the other three, cleared his throat nervously. Jack whirled around. "What?"

Ash mumbled something. Jack rolled his eyes and slowed down his walk so that the two Gryffindors passed him by and Ash was able to catch up with him. He raised an eyebrow: an invitation for Ash to repeat what he said. "I… uh… couldn't figure it out. I haven't started it either," Ash said.

Jack sighed and pinched the bridge of his nose. Rule 28 of the Time Agency: ALWAYS do your paperwork. It allows your superiors to know if and how time was changed due to your intervention. It also ensured they knew how you operated so that they could pair you with the correct partner during specific missions. Surprisingly, considering the type of people hired by the Time Agency, they were the most meticulous agency out of any other government-funded organization when it came to documentation, recording everything from important details from the mission (eye witnesses, chronological events, locations, etc.), to whether any big events were inadvertently changed, to who banged whom where and whether it was good for all individuals involved. Jack had carried this habit over with him to Torchwood and it had translated easily into doing homework at Hogwarts.

Everyone else, though… well, frankly, it was worse than at Torchwood. At least there, he had Ianto to help him wrangle the other operatives into doing their paperwork. Nobody here seemed to do their homework (even with the Doctor, Jack had to re-explain why he had to do his work about once a week, though in fairness, usually when the Doctor actually sat down to do his work, it only took him a few minutes to finish it).

"Alright," he finally said. "Al," he raised his voice so the Gryffindor walking a bit ahead with the Doctor could hear, "we'll meet you in the library in ten minutes."

Al nodded and turned to the Doctor. "You gonna join us?" he asked hopefully; Jack was actually a rather good tutor, but the Doctor made things fun. He also knew a lot more of what was going on under the surface of the spell and could explain to Al why he had to cast the spell in such a manner.

The Doctor shrugged. "Maybe later. I've got Defense Against the Dark Arts in fifteen minutes."

The Doctor strolled into the library, waved at Madam Pince, and headed towards the wizarding census section of the library. After discovering how private it was, Jack fell in love with the area, so all their study parties were located there. The Doctor loved it for a similar but different reason: books seemed to be very good at absorbing stray psychic energy. Various parts of the library could be overwhelming as they became saturated and started leaking old emotions (especially on days like this, when he was hyper sensitive). But in unused areas like this, they created a pseudo-Zero Room. It was a welcome relief from all the emotions flying around a school filled with teenagers. He wished he could spend all his time there on days like this, but after some amount of time, his brain would be so desperate for external input, he would start to either hallucinate emotions, or he would start feeling his own as if they were someone else's. It would get very disturbing very quickly.

As expected, as he rounded a corner, he found Jack, Al, and Ash sitting around a table that they were all starting to think of as 'theirs'. Al had finished his assignment, and the parchment it was written on was haphazardly sticking out of his bag. There were a few Transfiguration textbooks on the table, and the Doctor smiled morosely. While it was true he frequently made appearances at study sessions to help Jack and Al figure out various assignments, more often than not, when he showed up, they wound up struggling on their Transfiguration homework, which always turned into discussing how transfiguration actually worked, which very quickly devolved into arguments between Jack and the Doctor about just biting the bullet and learning the skill without understanding the theory.

While waiting for the Doctor to show up, Jack and Al were helping Ash with his homework. If the Doctor were to sit down at the table now, Ash would suddenly remember something he absolutely had to do and would leave. If it were anyone else, the Doctor would have taken a certain amount of joy in messing with him and would have sat down immediately. But Ash was honestly trying to get over his discomfort around the Doctor (it was hard going against everything his parents told him about which crowds to mingle with and would take more time). Moreover, despite taking meticulous notes in class, thoroughly reviewing textbooks, and constant visits to professor's office hours, Ash was still barely keeping up. He depended on Jack and Al to help him with his homework, and if the Doctor were to scare him away now, he would not finish the assignment, would get a bad grade on it, and most likely would never learn the information. The Doctor could not, would not do that to someone who honestly wanted to learn. The Doctor wandered around the stacks nearby and made sure the three students at the table did not see him (though Jack probably knew he was there anyway).

Finally, Ash sighed with relief and rolled up his parchment. "Thanks, guys," he said, carefully placing the scroll into a custom-made wooden tube (Ash insisted they were much more popular in France, where his father was from). "I really don't know what I'd do without you."

"Probably spend a lot more time with Richard and Leslie," Jack said. Ash considered it and shrugged noncommittally.

The Doctor chose this moment to appear from behind the stack he was browsing. "Hello, sorry I'm late. I got distracted," he lied. He settled into a chair. He briefly felt a wave of knowing amusement from Jack, confirming the Doctor's suspicions that he already knew he was there, but it was quickly grounded out by all the census books around them. The Doctor felt a flash of relief (his own emotion, for once today): clearly Jack was no longer as stressed out as earlier. It meant he would not have to play psychiatrist today, when he was incapable. One of these days though, he intended to get to the bottom of Jack's mental anguish.

"So… who needs to do their Transfiguration homework?" he asked. "It's due on Monday for Gryffindor."

"Same for Slytherin," said Jack, pulling out his partially completely homework.

The Doctor felt a familiar surge of emotion from Ash: prickly orange discomfort. It faded into the census books. "Actually, I have… I think I'm supposed to be meeting with Madam Hooch right now," he said, gathering up his supplies. It was a lie. The Doctor did not even need his sense of empathy to tell; Jack and even Al knew it also. What was curious though, was the cold, wet rag of shame that draped itself over Ash before it too was absorbed by the books around them. Shame? Shame about his prejudices? Perhaps Ash would come around sooner than any of them expected.

Ash quickly and neatly gathered his things and left the library. The three left all sighed, but none of them said anything: they had rehashed their conversation about Ash leaving so many times, there was nothing left to say. They started their Transfiguration homework. They were just starting switching spells (to the Doctor's intense dissatisfaction: he still had not figured out how transforming a wooden match to a metal needle worked).

For a while, they worked in relative silence, only speaking to ask a quick question, which resulted in a flurry of checking notes and textbooks before lapsing back into quiet. Then, suddenly, the Doctor spoke up. "Jack, how do you think they get around the Heisenberg Uncertainty Principle?"

Jack barely managed to keep a groan from escaping his lips. He had hoped to avoid a conversation like this today: honestly, he was not even sure the Doctor could handle an argument with his current mental status. Not that the Doctor ever thought about his own well-being. "The same way a transmat works, I assume."

The Doctor shook his head emphatically. "No. A Heisenberg Compensator is a massive computer. Even for amongst my… erm… family," he said, shooting a furtive glance at Al, who, having had experience with Jack and the Doctor's arguments, was doing his best to ignore the conversation, "it takes up a huge amount of room. Otherwise, it couldn't hold all the information. That's why we personally stopped using transmats."

"Could it work the same way your TARDIS works?" asked Jack. He also glanced at Al. As far as either of the time travelers could tell, Al thought the TARDIS was the Doctor's pet at home. They tended to encourage this, but every so often, they would say something that just would not correlate with the idea. Al did not react though.

"She enters the Vortex. It's completely different."

"I don't see how you could know that when I switch two buttons with each other," Jack said, referring to their first attempts at a switching spell, "they are not going through the Vortex."

The Doctor bristled slightly. "May I remind you," he said, hotly, "that my people created the Vortex. You might be able to partially access it, but it is part of me. I can feel it. And—"

"Okay, calm down," Jack interrupted. Honestly, he was rather alarmed (and just a little amused) at how quickly the Doctor got angry lately. He supposed it made sense, between being de-aged and having all the mental problems, but understanding what was happening and know how to manage it were two separate things. They best he could do was to keep it from happening. "So not the Vortex then." He paused to think. "You mentioned there was a way wizards can teleport from one place to another?"

"Apparation," Al suddenly said.

"Sorry?" Jack turned to look at Al, surprised he was getting involved.

"It's called apparation," Al explained, "the teleporting that wizards can do. But you need a license to do it." He shrugged at Jack's startled look. He did not understand much of his friend's arguments, but he liked listening to them.

"Basically, you're turning your body into a tesseract. In essence, you're stepping out of the third dimension and into the fourth just long enough to step over to where you intended to go. But it takes intense focus. It only works because the person controlling the spell is traveling with it. If you were to send an inanimate, three-dimensional object into the fourth dimension that way, it would probably get torn apart. That is, by the way, one of the reasons the TARDIS is sentient," explained the Doctor.

Al and Jack stared at him. Finally, Jack said, "Do you mean… are wizards able to enter the Vortex without a vortex manipulator or something similar?"

The Doctor stared at Jack like he was an idiot. "Okay, first off, Jack, your vortex manipulator does not allow you to enter the Vortex. You barely skip off of it. I've said it before, I'll say it again: you basically have a space hopper." Jack frowned slightly and touched his vortex manipulator as if to reassure himself it was just as awesome as he usually considered it. "No, wizards are not entering the Vortex. That would be messy. I'd probably crash into them at some point, and then they'd be splattered all over the TARDIS. They're mentally recreating themselves into fourth dimensional beings and then going back to third dimensional beings. They can only maintain it for perhaps a nanosecond, but because they spent a brief moment of time in the fourth dimension, they can choose where to… condense so to speak."

Jack shook his head. "I still don't understand how that's not the same as entering the Vortex."

"Because they're not entering the bloody Vortex!" the Doctor shouted. There was a pregnant pause as all three of them checked around to make sure they did not disturb anyone and that Madam Pince was not about to throw them out of the library. The Doctor continued in a much quieter hiss. "They're folding space. Maybe, MAYBE if they tried to fold time at the same time as they folded space, they'd get close enough to skip off the Vortex, like your manipulator does, but it would be exhausting, foolish, and dangerous. My point is, you need a conscious brain behind the process to make it work, which means it's not how switching spells work."

"Well then, I don't know, Doctor," said Jack.

"No, of course you don't. McGonagall has a lot to answer for," said the Doctor, standing up.

"Where are you going?" asked Jack, exasperated, already guessing the answer.

"McGonagall. Where else? She will answer my questions this time." The Doctor stalked off, leaving all his things at the table.

Al looked at Jack. "Did you understand any of that?" he asked.

Jack shrugged. "Some. Will you be able to bring his stuff back to Gryffindor Tower?"

Al nodded. "Of course." They turned back to their work. Jack idly wondered if the Doctor would manage, by the end of the year, to finish a Transfiguration assignment without arguing with Professor McGonagall.

A/N: Yay science! My excuse is I was surrounded by a bunch of PhD students at the time, all of whom are studying quantum chemistry and physics.

The next guaranteed update is January 3rd. I actually have handwritten 60 pages these last two weeks... sadly, it was all notes for class :P I am hoping (NOT PROMISING) to get a lot of De-Aged written soon, though, as winter break is in 2 weeks (THANK GOD!).

If you're wondering about the Supernatural story, yes it is still a thing, I just need the time/motivation to get the first chunk uploaded (again, it will not be regularly updated, so yeah, it will show up in huge chunks).

I kid you not when I say that reviews are the bright points of my days :) Thank you everyone for your support!

EDIT: continuity error. At this point, the Doctor does not know about time turners and therefore could not hypothesize that if a wizard used one at the same time as apparating that they would skip off the vortex