Harry was somewhat apprehensive when he went to his first Arithmancy class with Professor Vector. The textbook for the class had a lot of math in it, and math was never one of Harry's strongest subjects (although it was amusing to note that even magic, as divorced as it was from muggle sciences, could not escape mathematics). That thought turned out to be right on the money.

Vector began speaking as soon as everyone had arrived to her classroom, which was mostly bare save for a large chalkboard.

"Welcome, new students. This is the Arithmancy class for third year Ravenclaws. If this is not the class you signed up for last year, then I suggest you leave now, and find the class you did sign up for."

None of the students moved, so she continued speaking.

"Arithmancy, as all of you should know from the course selection sheet, is the study of wand based magic. It is the foundation from which all wand based spells are derived. Every spell, from something as simple as the Jelly Legs curse, to something as complicated as the Fidelius charm, operates on the basic principles of Arithmancy.

I imagine that a great many of you were looking forward to this class with a great deal of excitement, hoping to craft your own library of spells. While I do not hope to dampen your enthusiasm for the subject, I must inform you that the majority of wizards working in the field do not succeed in wholly creating a new spell that is useful enough to be commonly used by anyone besides themselves. While there have been, and always will be wizards who are particularly proficient in Arithmancy, to the point where they invent several or more spells, they are quite rare, and it would be amiss of me to expect that every single one of you will graduate to become a prodigy in the field.

There is a saying, that great work is done by those standing on the shoulders of giants. It is also true that many of the spells you use today were not developed by one wizard in one lifetime, but were the results of many wizards working in tandem over the years to create and refine the equations needed to produce the best results. If you end up not being the one to finish the work you start on, then do not despair, since there have been many wizards in your position whose contribution to their work was quite significant."

Vector took a deep breath before addressing the class once again.

"To learn Arithmancy, you will need to start with mathematics. Yes, math. The fundamentals of Arithmancy are all based on mathematics. I trust that all of you already have a basic grasp on basic arithmetic, although some of you may find that your previous education on the subject to be... lacking. We will be covering algebra this year. I hope that all of you have already read the first chapter of your textbooks."

There was some embarrassed muttering as some students realized they hadn't done so.

"To start off, I'd like you to take a look at this graph," Vector continued, drawing two lines intersecting on the chalkboard. "This one is what we call the x-axis, and this one, the y-axis..."

For once, Harry was glad that he had learned as much math as he had in muggle schools, as several of the presumably pureblooded students looked to be completely out of their depth.

By contrast, Muggle Studies was as uninteresting as Harry suspected it might be. Taught by Professor Burbage, it focused on all the broad details of muggle life that escaped many wizards. Harry had little to learn there, but it still beat getting his fingers chewed on by magical creatures, or poring over dusty old runes. He figured that he could use a class to keep up with the work from Transfiguration and Arithmancy, at any rate.

Then there was Professor Lupin, who continued the Defense Against the Dark Arts tradition of teaching about incredibly dull magical creatures and the best ways of dealing with them. The only interesting lesson he offered was on boggarts, peculiar creatures who could assume the form of the worst fear of the person who encountered them. That would, in theory, make them incredibly dangerous, if they weren't able to be disabled through a ridiculously easy spell.

Lupin even had a live one for them to practice on. Harry was curious to see what form the boggart would take on for him.

After the other students had their time with the boggart (producing such creatures as vampires, inferi, and Sirius Black), it was Harry's turn. Lupin seemed to move forward, but stopped when he saw what the boggart was.

It was Harry, at first, but then it clutched at its arm, and fell. Harry could guess what it was, some kind of failure of the circulatory system. A heart attack, a stroke, some kind of blood clotting or blood vessel rupturing that left him immediately dead or incapacitated, forever paralyzed or brain damaged with no way to recover, until another took him to the grave, the result of his sedentary lifestyle catching up with him...

"Riddikulus!"

And then the boggart was no longer Harry, but a chicken doing a silly dance.

Harry had sent a letter to Dumbledore asking about Slytherin's memoirs early in the year, and received a prompt reply shortly afterward. As it turned out, they contained, among other things, the secrets of how parseltongue was developed. However, Dumbledore said that a fully translated version wouldn't be available for another year, as there weren't many wizards with a working knowledge of old English to do the job. It was something to look forward to, at the very least.

While Harry kept himself busy with his schoolwork, and reading, the rest of the school was constantly focused on Sirius Black. For some reason, he never ceased to hold the public's attention, as rumored sightings of him flew in every week, from every part of the country. It really made Harry wonder why one escaped criminal was enough to freak out every person to make up such outrageous stories. What would these people do if they ever heard of the concept of parole?

Everything that year seemed normal until Halloween night, when an equally outrageous incident happened. Someone had slashed up the portrait for Gryffindor tower, leaving the occupant a weeping mess. The culprit was said to be Sirius Black, which Harry did not believe at first, given that the evidence was given by Peeves, of all people. Why would Black want to invade Hogwarts, which was guarded so heavily by Dementors, just to break into one of the dormitories? And, if he had been a student at Hogwarts previously, why would he try to assault the portrait instead of snooping around until he figured out the password needed to get in? If he had a way of getting into the castle undetected, then surely listening whenever a student opened the door would be no challenge at all?

Nevertheless, the Fat Lady's own testimony matched what Peeves had said, leaving little doubt that her assailant was Black. Harry concluded that Azkaban must have rotted the man's mind beyond repair... or it simply hadn't been that functional to begin with. It made him much more worried whenever he walked the corridors of the castle, knowing that an insane serial murderer could be hiding there at any moment. At least he wasn't trying to break into the Ravenclaw tower.

This fear was somewhat tampered when he noticed a number of older students and teachers that seemed to be following him around. Professor Flitwick eventually took it upon himself to explain what was going on to Harry, after the end of one Charms class.

"A moment, if you would please?" Flitwick said, looking right at Harry.

Harry walked up to the professor's desk.

"You might be wondering why the school has assigned escorts to watch you in the halls," Flitwick said. "That is because we suspect it to be the case that Black has made it his duty to hunt down and kill you."

"You do? Why?" Harry asked.

"Black was always a good friend of your parents, Potter. His betrayal of them led us to believe that he must have hated them a great deal. Before he escaped from Azkaban, he was known to be whispering, 'He's at Hogwarts.' We believe that, well, he wants to finish the job."

"Then why'd he try to break into Gryffindor tower?"

Flitwick rubbed his brow. "It may be the case that he believed you would be in Gryffindor, since both of your parents were as well."

"I doubt it," Harry said. "If he wanted to kill me, he should have done so thirteen years ago, instead of running off to kill Peter Pettigrew. I think it's much more likely that the man is clinically insane, and is breaking into the school for no understandable reason."

"Perhaps. Still, try to be careful."

"I will."