Disclaimer: The characters are not mine. I own nothing.

This story is a sequel to The House of Deduction. It may not be necessary to read it, as it is set years before (first year) but it will give backstory, and sets the story. And everything will probably make more sense if you do, so I suggest going to read that first actually.

The Art of Cunning

Chapter One

The Beginning of the End

Everything was normal at the Gryffindor table that breakfast, not even the Slytherin sitting surrounded by red and gold was a strange affair. As Sherlock Holmes more often than not, ate with the Gryffindors instead of his own house, and had been doing so for years. The Gryffindors had stopped throwing a fuss over it. The first years were always very confused to find a Slytherin at their table, but it was well into Sherlock's sixth year, and they were used to it by now.

Sherlock wasn't eating, he didn't eat breakfast, and no matter what John said, he wasn't about to start. He glanced up from his book, to see John frowning at him, Sherlock shook his head. "No," he said simply. John gave a resigned sigh, and picked up his piece of toast.

"Oi freak, pass the salt."

"Are you sure you want me to?" Sherlock drawled at him, putting his book to the side. "I might contaminant it after all," despite almost becoming an honorary Gryffindor member, Sally Donnovan continued with her open dislike of him, she was not the only one, although a collection of Gryffindors tolerated him for John's sake. He did however pick it up and pass it sideways to her. "By the way Donnovan," he said with a sideways glance. "If you are going to sneak out to snog, surely even you could do better than Anderson."

She spluttered at him, holding tightly onto the salt shaker and just staring at him. "Mind your own business freak," she scowled.

"I will admit," Sherlock continued as if she hadn't spoken. Beside him John sighed, but continued to eat, he had a feeling breakfast was going to end shortly. "I'm quite surprised, I thought us Slytherins were beneath you."

"Us Slytherins is it still?" she asked, tilting her head to the side.

He rolled her eyes. "You might be stupid, but I didn't think you were blind, my tie is still green and silver, it is still my house. Whether or not I spend time with you Gryffindors, I still hold the Slytherin traits, they do not disappear because I sit at a different table."

"Yeah, traits like evil and nutcases," she muttered under her breath.

Sherlock raised an eyebrow. "At least I'm not ignorant and stupid," he picked up his book. "But I'll pass that onto Anderson shall I? I'm sure he'll appreciate what you think of him. Come on John."

Donnovan sent Sherlock a scathing look. "He treats you like a dog," she said to John, who ignored her and followed Sherlock out of the great hall. "You could at least deny it!" she yelled after Sherlock.

"Why are you frowning?" John asked, glancing sideways from his notes to Sherlock, who had an empty page in front of him and was staring at the wall. Not appearing to be paying the slightest bit of attention to Professor Hudson, but knowing Sherlock he probably was. "I know that frown, and you have no reason for it. Nothing's happened," he narrowed his eyes slightly. "Has it?"

Sherlock shook his head at his friend. "No," he said. "But that is the whole point. He doesn't usually take this long to start something."

"Maybe he graduated last year?"

The he that they were talking about was Richard Brook, the illustrious note writer that Sherlock had been passing notes with since first year. Of course then, they hadn't known who he was. Only the initials, the course of the events of that year led them to his last name, and it was when Sherlock connected that the Brook, Professor Hope had been talking about, was the RB that he had been writing notes with all year, they found us his first name.

Not that it was any use at all, no matter how they had searched there was no Richard Brooks, certainly not at Hogwarts. And both Sherlock and John were convinced that he was a Hogwarts student. He had also been at the root of almost every event Sherlock and John had been involved in since they started Hogwarts.

"No."

"And how do you know that?" It was obvious by his voice that he was thinking that despite his knowledge, Sherlock didn't know everything.

"If it was his last year, he would have left with a bang. He's been playing with us all these years, he had some grand plan up his sleeve," he frowned, thrumming his fingers on the table. "He's either in our year, or the year above, how hard can it be to find him?"

The answer was impossible, because five years later they still had no clue.

John frowned at him. "Only you would be worried by inactivity Sherlock."

"I shouldn't be, the calm before the storm John."

"You're just bored," he accused.

"That too," Sherlock admitted.

"Mr Watson, Mr Holmes, if you could pay attention?" Professor Hudson was staring at them, as was part of the class now that they had been called up on talking.

"Sorry Professor," they chorused.

"Password?" The Fat Lady said, eyeing Sherlock and John, she was not particularly fond of allowing other houses into the common room, especially Slytherins. But she had resigned herself that if anyone was the exception to the rule it was Sherlock Holmes. He practically lived in the common room anyway.

"Leo corde," Sherlock answered before John even opened his mouth, the portrait swung open, and the two boys entered. They found Mike and Carl sitting in chairs near the fire and joined them, the two Gryffindors grinned at them, John grinned back, and Sherlock gave a small smile.

"We could do with some of your potions help here Sherlock," Carl said with a gesture towards a half written potions essay sitting in front of him. "Merlin knows you read enough potions books to be able to recite them off the top of your head."

"And his brilliant memory doesn't hurt either," Mike added under his breath.

"You really could just go for your Newts this year, you'd probably pass."

"With flying colours."

"Oh stop it you two," John said with a shake of his head. "Do your own homework you slackers."

"Well that's just boring isn't it?" Carl said wrinkling his nose.

Sherlock snorted.

Thinking that John should have gone into Hufflepuff so he didn't need to walk down seven flights of stairs, Sherlock headed back to the Slytherin common room. He was pushing it, and would only just get there in time for curfew, if he was lucky.

He tended to avoid his common room as much as possible, he had nothing against the room itself, in fact he quite liked it, but the people were another matter completely.

Giving the wall the password he entered the common room, to find it empty, with the exception of Sebastian Moran and Jim Moriarty sitting on a couch doing homework.

Jim glanced up at the sound of Sherlock's footsteps. "Out again Holmes?" he asked, there was a mocking hint to his voice, the two never outwardly argued or were hostile to each other, but there was a hint of something else behind their words.

"Obviously," Sherlock replied with an eye roll. "Why ask questions you know the answer to Moriarty?"

"I am a prefect you know, I could perfectly well put you in detention for breaching curfew."

"You do that then," Sherlock answered, heading towards the dorms.

Jim just grinned at him.

The problem Sherlock thought, with sharing a dorm with people he knew that he couldn't trust, was that he always had to be careful. Careful what he said around Moriarty and Moran. Careful that he wasn't going to get a black eye around Anderson and Wilkes. Mycroft had left the school two years previous, and with it the threat of bad things happening if one attacked his younger brother.

Fourth year had been a bad year all round. Especially when one added in the werewolf.

At least Anderson had stopped trying to creep up on him in the night when Sherlock had put a protective spell around his bed, and Anderson had gotten such a shock that he couldn't sit down for a week.

It wasn't really a surprise that he spent more time with John and the Gryffindors, at least they were honest about the fact that they didn't like him.

After dinner the next evening instead of heading up to Gryffindor tower with John, Sherlock headed back down to the dungeons, but to the potions classroom rather than his common room. Some years previous Slughorn had opened an offer for Sherlock to use the potions room in his spare time if he wanted to. Mostly just to stop him experimenting in class, when he was supposed to be doing class work. Sherlock was the only one still exploding cauldrons, despite the fact that he was the best potionier in the class, simply because his experiments weren't always sound.

He entered the classroom to find it empty, more often than not it was, Slughorn used to oversee it when he was in the classroom, but these years later he trusted Sherlock enough to not need a guardian sitting there and watching.

He opened his notebook, and gathered the ingredients for a potion that he was working on and set to work, making adjustments to his method as he went along.

"Try stirring it clockwise."

Where anyone else might have jumped a foot in the air, Sherlock simply nodded, he had noticed the Severus Snape slink into a portrait on the wall a few minutes previous. "Aha," he said with a smile, as stirring it clockwise as opposed to anti-clockwise lightened the colour to the sky blue colour that he was aiming for.

"You would have more success if you altered other potions to suit your needs instead of trying to make them from scratch."

"Possibly," Sherlock murmured adding a pinch of sodium dichromate to the mixture. "They don't work as well however when you are using muggle chemicals instead of just magical plants. If I start from scratch, I have to think about the cause and affect, whether than learn it when I add the wrong ingre-" he didn't get to finish his sentence as the potion started to bubble and overflow.

Cursing he scrambled for his wand and vanished the whole lot. With a sigh he turned back to his notes.

Severus snorted. "Magic and chemistry is not to meant to mix Holmes, there is a reason your potions aren't working as planned."

"I'll get them to," he muttered stubbornly. Though he had a feeling Severus could be right, it was too unstable, magical properties cancelling out the chemical ones, and the chemicals changing the properties of the magical ones. It needed years of research before it was likely to be able to be used. To figure out how the combinations of chemicals and magical ingredients interacted.

I hope everyone enjoyed the first chapter, and enjoys the rest of the fic. (If you do, don't hesitate to review.)