Disclaimer: This story is based on characters and situations created and owned by JK Rowling. No money is being made and no copyright or trademark infringement is intended.

A/N: Thanks to my beta Lathea and thanks to all reviewers!

Rectifier

Chapter 12: Mind Game

The sixth years had their first Defence Class on Thursday. Like other NEWTs classes, students from all four houses were having lessons together.

Theodore Nott sat near the back of the classroom, idly watching the other students as they chatted among themselves. Given the standard of their previous Defense professors, he was surprised at the number of students who managed to get into the advanced class. He had expected Potter and his gang to be here, along with several Ravenclaws, but Neville Longbottom? There were also quite a few Hufflepuffs in the room.

Aside from Theo himself, the only other Slytherin sixth years in advanced Defense were Draco Malfoy and Blaise Zabini, making Slytherin the least represented house in this class – a fact that Theo found quite amusing. With the war going on, no one in this school, except maybe Potter, needed lessons in Defense more than the Slytherins. But as always, Theo seemed to be the only one who could see that.

Of course, one could always learn from books, but it wouldn't hurt to have a teacher who knew the subject. And judging from what he had heard from the first years yesterday, Theo had a feeling that Dumbledore might have finally run out of options and actually hired someone who wasn't a complete idiot this year.

The class fell silent when the door opened and their professor strode in. Theo blinked once in surprise.

"Is that the Sorting hat?" a Hufflepuff sitting behind him whispered.

"Yes, and it sure doesn't look happy," came a reply in an equally low voice. "I wonder what it's here for."

Indeed, Kray was carrying the Sorting hat in his hands. The dusty old hat looked annoyed as it was set on the teacher's bench. In fact, Theo had an impression that it was currently glaring at Kray, who, contrary to the hat, looked quite cheerful.

"Good morning, class," he begun. "You have all gained at least an 'E' in your Defense Against the Dark Arts OWLs despite the professors you've had in the past, so I'm going to assume that you're either very talented, or you're interested enough in this subject to do some self-studying on your own." Several students in the class exchanged glances, none of them were Slytherins. "This is a NEWTs class, meaning that you're done learning how to conjure a proper shield or how to identify one dark creature from another. This year, you'll learn skills that combine the knowledge of everything you've learned so far. I can guarantee that my lessons are going to be much harder and dangerous than what they used to be, so I expect every one of you to be fully prepared, and that includes extra practice and studying on your own."

Kray seemed to be the kind of person that could capture his audience's attention without any visible efforts, Theo noted.

"There's much I'd like you to learn, but unfortunately, it seems your previous professors have neglected to teach you some of the most basic skills in Defense Against the Dark Arts. We cannot proceed without those skills, and I plan to use less than a month's time to remedy that."

Kray picked up the Sorting hat again. "The Headmaster is generous enough to let me borrow the Sorting hat for this class," a hint of smugness slipped into the professor's voice. "The Sorting hat originally belonged to Godric Gryffindor, but it – ah, my apology – he," Kray corrected himself, glancing at the dirty old hat, "was charmed to keep everything he learns from the students' mind a secret, under any circumstances. The Sorting hat wouldn't say a word to the Headmaster, or in fact, the Founders themselves, even if the student in question is planning to become the next Dark Lord."

Theo thought he saw Potter's back stiffened.

"As such," Kray went on, "the Sorting hat is perfect for you to practice Occlumency."

Theo's eyebrows shot up. Occlumency was an obscure branch of magic that most were not aware of. It was not Dark Arts, but it certainly wasn't the kind of magic that a teacher – especially a teacher hired by Dumbledore – would teach in a class.

"I see some of you recognize that name," said Kray. "Who can tell the class what Occlumency is? I'll give you a bonus point if you can name the kind of magic it specifically defenses against."

That would be Legilimency, Theo answered mentally, watching as Hermione Granger's hand shot up in the air. He sat up straighter in his seat. It seemed his intuition about the new professor had been correct. Finally, he was going to learn something new in his Defense class.

Harry had known Riddle was planning to teach them Occlumency, so he wasn't too surprised when he heard what they would be learning in their first Defense lesson. He hadn't expected Riddle to use the Sorting hat, of all things, as a mean for them to practice though, but he wasn't about to complain. After the way Riddle had terrorized the first years yesterday, Harry had half-expected Riddle to start throwing Legilimens at them without warning.

"Control your thoughts, clear your mind."

Harry tensed at Riddle's voice. Having his eyes closed while being in the same room as Tom Riddle – who had everyone doing some kind of meditation exercise - was putting him on edge, to put it mildly. His scar had started burning the moment Riddle stepped into the room, and he was close to pulling out his wand at any moment now.

Riddle must be using Occlumency though, since his scar didn't hurt as much as it had in Dumbledore's office a few days ago.

Harry shook his head, pushing away his thoughts. He would never learn Occlumency at this rate. Not that he really expected to with Riddle as his instructor.

"If you have trouble clearing your mind, try to find an object to focus your thoughts on," came Riddle's voice again. Harry had to struggle just to keep his eyes close. "It could be anything - a picture, a song, or even a paragraph from Hogwarts: A History - as long as it can keep your mind focused."

An object to focus his thoughts on? The image of Draco Malfoy jumped into Harry's mind; he had been trying to prove that Malfoy was a Death Eater since running into the blonde in Diagon Alley. But he could hardly use that to practice Occlumency, could he?

What else then could help him focus then? It had to be something that had nothing to do with Voldemort or Death Eaters, so that left…

Of course, Quidditch.

Harry tried to picture the Quidditch pitch in his mind. The goal posts. The scoring area. The audience stands with different house colors. He imagined himself flying on his broom, overlooking the pitch.

To his left, something glittered under the sunlight. He immediately chased after it, calling forth the concentration that had always come naturally during Quidditch matches.

He didn't notice that the imaginary Quidditch pitch had faded from his view, along with every other thought in his mind. He eyes focused solely on the golden snitch, flying just inches away from his reach –

"- think you're ready, you may open your eyes, but keep your mind focused."

Harry jumped and blinked a few times as opened his eyes. He realized with a start that he had, for the first time, managed to keep his mind free of all thoughts. The pain in his scar also seemed to have faded a little. Was this what Snape had meant by 'clearing his mind'?

He looked around the classroom. Several students still had their eyes closed, including Ron. The redhead furrowed his brows, either in concentration or in confusion as to what he was supposed to do.

Looking away from Ron, Harry found himself staring straight into the eyes of Tom Riddle, who was standing near the back of the classroom. Startled, his concentration slipped and a sharp pain immediately erupted from his scar.

Frustrated, Harry worked to clear his mind again. He pictured the golden snitch, flying slightly ahead of him. He concentrated only on the image and let all other thoughts faded back to the depth of his mind. It was harder than it had been before, but slowly and surely the pain in his scar lessened to a more bearable level. To Harry's surprise, he saw Riddle nodding his head in approval.

Riddle broke eye contact seconds later and turned his attention to another student. Harry took the chance to study his new professor.

His identity aside, Riddle's lesson wasn't anything like he had imagined. For one, Riddle seemed to have quite a lot of experience in teaching. And as he watched Riddle bending down to explain something to Neville, Harry had a feeling that Riddle actually liked teaching them, which was highly unsettling, as far as he was concerned.

It took ten more minutes before Riddle was satisfied with their progress. He walked back to the front of the class and addressed them all again.

"Keeping your mind clear of all private thoughts is a conscious effort. If you're doing it right, then your magic should respond to that effort naturally by forming a shield around your mind," explained Riddle. "But Occlumency is a branch of magic, not some kind of calming technique, so our work here is not done yet. So far, you've formed a tentative shield around your mind. That shield can prevent you from projecting your thoughts out unconsciously, but it wouldn't hold when someone try to get in. Our next step is to strengthen it with magic, which is where the Sorting hat comes in." The Sorting hat huffed indignantly, but Riddle ignored it. "When I call your name, you will come up here and put on the hat, like you did during your sorting. If you've done the first step right, then you should be able to feel the hat trying to get into your mind. Remember that feeling and try to force back the invasion with your magic. I'll take questions after you've all tried the first round." Riddle paused briefly then added, "I believe this is the safest setting you can get to learn Occlumency. But if this exercise makes you feel too uncomfortable, you have the choice to hand in an extra essay instead for this class' mark. Anyone's leaving? No? Well then, let us begin."

Harry found it odd that Riddle would let them skip the whole practice, but he didn't have time to ponder on it since he was the first one Riddle was calling up front.

Harry sat down on the chair that Riddle had placed at the front of the class. He closed his eyes and Riddle put the Sorting hat on his head.

The hat was not speaking to him this time, nor was it dropping any weapons on top of his head. Harry waited, trying not to lose his focus. Then suddenly, he felt it.

It began with a light probe, against what must be the 'shield' Riddle had mentioned. Harry wasn't even aware that there was a shield until now.

The probing stopped, but only for a few seconds, then the attack came again, faster and harder than before. Remembering Riddle's instruction, Harry tried to push the invasion back. He could feel the shield protecting him getting thicker and stronger, but still the hat was forcing itself in, until-

Harry winced as the invading presence broke through his shield. And immediately he could hear a familiar voice speaking in his mind.

"That was not bad, not bad at all."

"You still managed to get in easy enough," replied Harry.

"Of course I managed to get in! What do you expect? Only a handful of wizards can hold me off, and never a student. Humph, I told Riddle this is a bad idea."

Harry's head snapped up. "You know who he is."

"Yes, I know who your professor is. Why else do you think he could talk me into this?"

"Because he is an heir of the Founders?"

An unmistakable hint of annoyance from the hat confirmed Harry's guess.

"Off you go now, the other students are waiting."

Harry pulled the hat off his head and handed it back to Riddle. He realized his forehead was covered in sweat, but the pain in his scar had disappeared almost completely. He looked up to see Riddle smiling at him.

"Five points to Gryffindor." At the shock on Harry's face Riddle's chuckled lightly before turning back to the class. "Mr. Longbottom, you're up next."

It was after dinner that night when Severus Snape heard of what Thomas Kray – if that was even his real name, which Severus doubted – had taught the sixth year students. Though no one would ever hear it from him, Severus had to admit that he was impressed.

First showing the first years the Unforgivables and now teaching the sixth years Occlumency. It was no wonder why Kray had caught the attention of both Dumbledore and the Dark Lord. And Severus' too, if he was honest with himself.

He had heard how Kray describe the Unforgivable Curses the night before. And he knew that only a man who had a deep knowledge in the Dark Arts – and not only defense - could talk about them the way Kray had.

Then Kray had taught the students Occlumency today, an art that only a few had knowledge of and was almost impossible to teach, as Severus' lessons with the Potter brat last year had proven. No one would willingly expose their mind to another, even to their teachers. So even though having guidance could significantly speed up the learning process, most Occlumens' were self-trained.

Kray had obviously found a way around that restriction; a very clever way, Severus admitted. But just how could a supposedly new professor, who had just come to Hogwarts this summer, think of using the Sorting hat as a tool for teaching? It was almost as though the man had been teaching at the school for years.

Walking along the quiet corridors of Hogwarts in his night patrol, Severus continued to ponder on what he had learned of the new defense professor. He held his wand high to light up the dark corridors, his eyes scanning every corner for students who were out of bed after curfew.

He had first assumed that Kray was a friend of Dumbledore's, or perhaps someone who had helped fighting the Dark Lord in the first war. But after watching how the two interact during mealtime, Severus was starting to have his doubts. They seemed to know each other very well, yet at the same time they acted as though they were only a step above strangers. Either one had to be an act, and Severus put his bet on the former.

What kind of game was Dumbledore playing at this time? Severus wondered. It had to be about the war, but how did Thomas Kray fit into the old wizard's scheme? And how did Kray fit into the Dark Lord's scheme, for that matter?

Severus still remembered the meeting just before school started. The Dark Lord had almost looked… shocked when Severus informed him of Dumbledore's latest choice of Defense Against the Dark Arts professor. He had then been asked to recount everything concerning Kray in details, including the man's appearance. The Dark Lord rarely showed such interest – obsession , even - aside from news concerning Potter.

Severus stopped in his track as he caught sight of a flicker of light coming from the end of the corridor. A student was out of bed. Was it Potter? It was typical for the boy to break school rules on the first week of class.

The sole other light source other than the light from Severus' wand was coming closer, towards where Severus was standing. Fool, though Severus as he extinguished the light of his wand and waited in the darkness.

But it was not a student that was lingering in the corridor after curfew, but the subject of Severus' earlier musing.

"Ah, Professor Snape."

Thomas Kray was holding his lightened wand in one hand, balancing a pile of books in another. Severus narrowed his eyes; years of being a spy told him that the surprise on Kray's face was feigned.

"I don't seem to remember you being on patrol duty tonight, Professor Kray."

"No, I'm not. I was merely searching for books in the library," said Kray calmly. "It seems I have lost track of time."

The library was supposed to be closed at this hour, to the students and the staff. So Kray thought he was above rules then?

Severus' gaze fell onto the pile of books in Kray's arm and raised an eyebrow. "I wasn't aware you're interested in curse breaking."

Kray met Severus' eyes. Something about the calculating glint in the pair of deep blue eyes sent a shiver down Severus' spine. He unconsciously tightened his grip on his wand.

"I would think it is a mutual interest, Professor Snape."

Severus narrowed his eyes. "That curse is unbreakable."

"I am known to do the impossible," countered Kray swiftly. How arrogant was this man?

Severus could feel his annoyance rising, but he had to ask. "Have you found out anything?"

"I'm not in the habit of discussing unfinished work with those unrelated to my project," replied Kray. "Unless you'd like to assist? I could use the knowledge of a Potion Master."

Severus was tempted to curse the man, and Kray looked as though he knew exactly that.

"But I think I've delayed you long enough, Professor Snape. If you're interested in this little project of mine, you should be able to find me reading in my office all night." With a curt nod, Kray walked past Severus and disappeared down the corridor.

Severus stared after him with gritted teeth. He had a feeling that this whole encounter had not been an accident at all. To add to his annoyance, he knew Kray's invitation was not one that he could ignore.