Striking Thirteen
Long merely spoken of as 'the mystery story,' I've finally got round to posting this. Updates will henceforth be posted once a week. Most of the time, anway. Honestly, this whole thing is in a constant state of editing. Don't be surprised if you re-read and find I've changed something. But it won't be major.

Summary: Friday the 13th has some...interesting effects on magic. Harry deals with the consequences. Eventual HP/SS. Currently rated PG-13, if that, for a little bit of language. And no, there's no relation to 1984 beyond the origin of the title.

Theory that first appears in Chapter 5 is from here, but I've poked it a bit to suit my purposes.

Special thanks to the lovely _ataraxis_for beta-reading!

Table of Contents:
Prologue
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10: in progress

Striking Thirteen

Prologue

Due to the strange way that spells were wont to act on Friday the 13th, Severus Snape ought to have cancelled the Duelling Club meeting that evening. He had determined, however (with no small quantity of characteristic sadism), that it would be a good learning experience for the students to experience it first-hand.

After sending students to the Hospital Wing for four consecutive weeks, Neville Longbottom ought to have had the sense to quit the Duelling Club, for the safety of his fellow students if nothing else. Harry Potter ought to have had the wherewithal to stay in bed, or at least to have gone back to bed after falling off his broom twice in Quidditch practise that morning. Both being Gryffindors, however, neither of these boys had much sense at all, especially when it came to backing down in the face of adversity. The phrase "back down" wasn't even in Harry's vocabulary, except when preceded by "won't" or "never" or "Voldemort will," and Neville's Gran had long ago instilled in him that no one likes a quitter. And Neville wanted people to like him.

And Snape, being a Slytherin, or perhaps just being Snape, neglected to inform the Club members of which spells they absolutely must not cast that day because of the way the date would affect them. He decided to operate on the (patently incorrect) assumption that the students should already have learnt them.

At the Duelling Club meeting, Harry's luck continued to go downhill. The little magical wheel that spun to determine the partnerships for the evening paired him with none other than Neville.

"Tonight's exercise," Snape began, "will be disabling your opponent with defensive spells only. You cannot curse your opponent directly; only reflect, bounce, or shield against his or her spells. You will each take a turn, assuming both of you survive the first round. You may begin."

Harry smiled. This was going to be obscenely easy--he felt confident that he could block anything Neville could throw, and he knew Neville's defensive spells weren't what they ought to be. Neville, on the other hand, looked mortified.

If Harry had had a bit more sense, he would have started the match himself. But he deferred to Neville to take the offensive first. He opened with a couple of wobbly hexes that Harry dodged easily. The third curse he threw, though, refused to be dodged. Harry tried, but it bounced off someone else's shield and hit him head-on. Just before everything went black, he heard Snape bellow, "Idiot boy! Do you know what you've just done?"

One

Harry awoke in the Hospital Wing, feeling as though his head had just been chewed on by a Manticore. He remembered now. He had been helping Severus test an experimental Celerity potion engineered from Vampire DNA. Clearly, it hadn't worked. Where was Severus, anyway? It wasn't like him not to be there when Harry was in hospital, particularly when Severus himself had helped put him there.

Harry raised his hand to massage his aching temples and instantly recoiled as though he'd been burned. The scar. The scar was there. It was back. What was it doing there? What had happened? "SEVERUS!" he yelled. Oh, dear sweet Merlin on rollerskates, his voice didn't sound right either. He struggled to get out of bed, but his legs wouldn't cooperate. "SEVERUS!" he shouted again.

The door opened. It was not Severus standing over him now, but…a ghost? The ten-years-dead figure of Albus Dumbledore stood over him, looking every bit as alive as he had the moment before he'd raised his wand to cast the final spell on Voldemort.

"Albus," Harry whispered, his eyes filling with tears. "What… how? I mean, you're…" And then it hit him. Somehow the potion had malfunctioned and sent him back in time. Which meant that somewhere in the future, the Harry of this time was stuck in his body. Oh, bugger. "Albus, you have to help me," he began, scarcely stopping to breathe. "There was a potions accident, I'm not who I look like I am. I mean, I'm me, but I'm in the wrong time and--"

Albus held up a hand, commanding him to stop. "Harry, I'm pleased to see you're awake, my dear boy. But there are a few details you do not know. You are exactly who you look like you are; however, you are not who you think you are. Tell me, Harry, what date is it?"

"Well, when the cauldron exploded, it was October thirteenth, but I'm not sure how long I've been out for."

"And the year?"

"2008." Clearly, Harry reasoned, Albus would have asked no such questions if he had thought Harry's answers would be correct.

Two

Harry awoke in the Hospital Wing, his head feeling as though it had been chewed on by a Manticore. Snape and a very contrite Neville were standing over him.

 "What happened?" Harry groaned, clutching his aching head.

 "Would you like to field that one, Mr. Longbottom?" Snape asked pointedly.

 Neville took a deep breath. "I tried to hit you with a Reductor curse, but because I'm an idiot Gryffindor, I failed to bother learning that on Friday the Thirteenth, some spells do not act properly, and it tried to turn into a Reve de Vie curse, which is what hit you."

 "And Mr. Potter is currently awake because?" Snape prodded.

Neville sighed. "Because I'm a mediocre wizard and the curse was too weak."

 "And?" Snape had clearly lectured him at great length while Harry had been unconscious.

 "And if the curse had worked, there would have been no counter-curse for twenty-four hours, during which time you would have spent lucidly dreaming one possibility of your future based on your desires, and you'd probably have gone mad."

 "And?"

 "And I'm going straight to the Ministry and have my wand snapped because I'm a danger to myself and the wizarding world." Neville seemed to have finished his instructed speech and began to stutter and blubber. "I'm-- I'm so s-sorry, Harry. I could have ruined your life when all you've ever tried to do is help me and--"

 "Neville, Neville, stop it. Just stop it." Harry sat up in bed, though his entire body ached. "Don't be ridiculous. There's no reason you ought to have your wand snapped. Everyone makes mistakes, Neville. I've made mistakes that have killed people, and I'm still here."

 "But you've got to stay, you've got to kill You-Know-Who--"

 "Voldemort," Harry corrected automatically, at the same moment that Snape said "The Dark Lord." They glared at each other.

 "I'm just nobody," Neville continued, tears still streaming down his round cheeks. "I'm no good to anyone," he said, his voice rising, "and I might just as well go and die!"

 "Neville!" Harry shouted. "That's enough! I don't know what Professor Snape has been telling you, but unless there's some law on the books that requires you to have your wand snapped, there's no bloody reason to do it!" He turned an icy glare on Snape. "Tell me, Professor, is there any such law?"

 "There is no such law, Mr. Potter, but there is a statute that enables the administrator of a school to have a student removed from wizarding society if he is a danger to others, which Mr. Longbottom plainly is."

 "The administrator! That's Dumbledore, Snape, not you, no matter what delusions of grandeur you may have!"

 "Fifty points from Gryffindor for your insubordination, Mr. Potter," Snape said as though he were remarking on the weather. "As you know, Professor Dumbledore is currently away, and as Deputy Headmaster--" Harry remembered with a pang McGonagall's death that summer-- "the decision-- the irrevocable decision--is mine."

Harry sneered at his Potions professor. "Two thousand points from Slytherin for being a heartless bastard." He waited for more points to be deducted now, but the words did not come.

 "Never presume to know my heart, Potter," Snape said in a low, flat tone, not breaking the stare.

They sat silently with their eyes locked for a long moment, each daring the other to move or breathe. Neither did until the all-but-forgotten Neville sneezed.

Snape whipped his head around. "Longbottom, go and say your goodbyes. Groundskeeper Filch will escort you to the Ministry in thirty minutes."

Neville turned and ran from the room with a sob. Harry opened fire. "How dare you, Snape, how bloody dare you? Neville's trying, he's really trying, and he's gotten better, even you must see that! He only made one stupid mistake, and nobody's hurt, so what fucking right have you to have him expelled and incapacitated after you've let Malfoy off with detention for ten times worse?"

Snape leaned down, pinning Harry back against the pillows, his face so close that Harry could smell the cinnamon on his breath and the sandalwood on his skin. "Because, Potter, Longbottom's no use to anyone--"

"Neither is Malfoy!"

"--And Longbottom's father is not out for my blood. And everyone's top priority is to eliminate any threat to you, which, in this case, even includes Longbottom. So if you want to lay blame, you may sleep soundly in the assurance that it rests entirely on your shoulders, my golden and shining saviour."

Snape had billowed out of the room before Harry had the chance to know what hit him. Weak, he slumped back into the pillows, and with utter horror brought his hand to the painful hardness between his legs.

Three

Albus explained everything and left Harry reeling. The last ten years of his life had been a dream. A total and utter lie. Nothing had happened. The curse that Neville had hit him with all those yesterdays ago actually had worked. Albus wasn't dead. Neville wasn't dead--or perhaps he was; Albus hadn't actually said. Voldemort was still there, undefeated and looming. And Severus... Severus was no longer Severus, but a dark and distant figure known as Professor Snape. He was seventeen, not twenty-seven. Hogsmeade had never been burnt to the ground. All this knowledge, his experience, all he had learned and said and done, it was all an infinite falsehood that unraveled before his stinging eyes. Nothing. He had nothing.

He turned over and buried his face in the pillows, hoping somehow he could block out the truth. "So nothing was real," he whispered when Albus was done.

Albus sat down on the bed and put a comforting hand on Harry's shoulder. "Not events. Wizards' dreams are unique, though, Harry. I'm sure you know that, given your connection with Voldemort. Tell me, did you acquire any new skills in your dream?"

Harry turned back to face Albus and nodded blankly, not sure where this was going.

"Everything in your dream, any book, any new spell, was something you had access to here. If you went to the library in your dream and looked at a book, you read something that was really there. It's a phenomenon known as latent acquired content."

Harry blinked. "So what you're saying is that everything I learned was real, just not anything I did."

"Essentially."

"So I've completed school. Why don't we just put everyone to sleep for a couple of days and have them do all their schooling there?"

"Think about that, Harry. Think about what you dreamed. Think about what would happen if everyone dreamed their own separate timelines."

"Everyone would go mad."

"It's very likely. Not many wizards have the power to survive such a thing. You do. I do. Perhaps most of the professors at this school do. But your average student wouldn't. And there's something to be said for tradition as well. Part of our job here is to mould you students into functional members of wizarding society. And we unfortunately cannot control dreams, so even if replacing schooling with lucid dreaming were a practical idea, there's no telling what would happen. Perhaps the possible timeline of a student's dream would include dropping out of school and spending the rest of his days reading Muggle comics. I, for one, once had a particularly pleasant dream in which I read the entire works of Charles Dickens. While enjoyable, it afforded me nothing in the way of practical knowledge."

Harry smiled slightly in spite of himself, but his mirth faded quickly. "What's going to be done about my schooling, then? I've finished it, but I couldn't exactly bring my N.E.W.T. results back with me," Harry said bitterly and with no small amount of sarcasm, thinking of a few other things he couldn't bring back either.

"That's quite simple. When you're strong enough, a special examiner from the Ministry will administer your N.E.W.T.s. Assuming you pass enough of them, you'll be free to do as you please. Tell me, did you complete a secondary course of study?"

"An apprenticeship."

"With?"

Harry sighed. Dumbledore was certainly going to know the story now. "Professor Snape," he mumbled.

Dumbledore smiled benignly, but Harry could practically see the wheels turning in the old man's head. "Well, there's no substitution for an apprenticeship, I'm afraid, but you may, of course, also sit the Potions Master certification test. You've a unique opportunity here, Harry. You've seen the life that resulted from one course of action. You now have the choice to repeat that course and live that life again, though it may not be exactly the same. Or you may choose another, if another would have been more satisfying. Tell me, Harry, were you happy?"

Four

Neville never made it to the Ministry. The house-elves found his lifeless body hanging from a rafter in the Great Hall. Though Harry was still weak, Madam Pomfrey was unable to stop him when he bounded out of bed in a blind rage and stormed into Snape's office.

"I hope you're happy," Harry hissed across the desk at his teacher.

Snape gave him a tired look. "No one could have known the boy would be so stupid. He could have led quite a comfortable life as the squib he was to become."

"You heard him threaten to kill himself!"

Snape sighed. "As a teacher of adolescents, you must realise that I have been hearing such threats at least twice a day for the past seventeen years. There has yet to be one that was serious, and I thought no differently in Mr. Longbottom's case."

"You'd bloody well take points from him posthumously if you could," Harry spat.

Snape leaned serenely back in his chair. "I did try," he said, "but there seems to be some spell in place preventing it."

"You complete bastard," Harry said, leaning as far into Snape's personal space as the desk would allow. "You made his life a living hell for six years, and were well started on a seventh. How can you presume to be so cavalier about a death you clearly helped cause?"

"I've killed more people by more direct means, as have you."

"I've never committed murder."

"If Bellatrix Lestrange's death wasn't a murder, then I'm Helga Hufflepuff."

"It was self-defence! I was cleared of all charges!"

"As was I, numerous times."

"Dumbledore didn't have to pull any strings for me."

Snape put a hand on his chest and gave him a push. "Sit down, Potter."

Surprised by the touch, Harry obeyed.

"Potter, I'm not going to stand for your Gryffindor Golden Boy insubordination any longer. You've defied me since the day you got here, hated me since you first laid eyes on me. You've no right to judge me on any basis. You are valuable to the Order's cause--nay, essential--which is why you were not expelled long ago. Despite your hero complex and your inflated ego, you've shown promise the past two years. You've mastered Occlumency and the Animagus transformation. And you've surpassed most of the students in my class."

Harry thought his eyes were going to bug out of his head. However backhanded it may have been, Snape had just paid him a compliment.

"Despite the fact that I can barely stand you, it would be criminal not to at least offer you the opportunity to develop your talents. Albus Dumbledore is mortal, Potter. I'm arguably even more so. If I even live to take his place at the head of this school, I will not be able to continue teaching Potions. As such--Potter, close your mouth, you look like a great bloody trout--as such, I must make provisions for my own successor. You, sadly enough, are the most promising candidate."

"Why me?"

"Potter, you idiot, I've just told you. Don't make me say it again; it was painful enough the first time."

"But why not hire someone who's already qualified?"

"I see Miss Granger must have failed to transmit the entire contents of Hogwarts: A History to you. Since the time of Salazar Slytherin himself, there has not been a master of these dungeons without Slytherin blood. Some intangible and unbreakable ward set by Slytherin refuses to allow them to be mastered by someone who is not one of his own."

"I don't have Slytherin blood."

"Even if you didn't, the Dark Lord's transference would have done well enough."

"Even if I didn't?"

"I'm pleased to see you can hear after all. Yes, Potter, you may take that to mean that you do, in fact, have Slytherin blood. Very little, but enough."

"How?"

"Your mother's paternal grandparents were wizards. Her father was a squib who married a Muggle. Her sister, we ultimately discovered, had an entirely different father, a Muggle, and so was born a Muggle herself."

"Why didn't anyone tell me?"

Snape shrugged as though Harry had just asked him why the sky was blue. "You had no need to know. I highly doubt anyone but your grandmother knew Petunia Evans' parentage, and no one but your grandfather knew that his parents were wizards. We--the Order, that is--only found out by chance when we performed the initial tests to assure that your mother and your aunt were blood-related. We found that they were, but only on one parents' side, so we researched it further."

"I don't suppose it's that important after all," Harry said, long resigned at this point to finding out new and interesting facts about himself every day.

"As to your taking over my position when the time comes, it will require an intensive apprenticeship to begin immediately."

Once Harry and Snape had agreed on a time for their first meeting, Harry left the dungeons. It was only when he reached the end of the corridor that he realised it had never occurred to him to refuse, stunned as he had been by the offer. He also seemed to have entirely lost the thread of his anger over Neville's death, which had, as he now remembered, been his reason for being in the Dungeons in the first place. Damn Snape had distracted him. And he absolutely refused to think about exactly why.