DISCLAIMER: I own nothing but this twisted so-called "plot".

Some of the dialogue here has been directly lifted (errrr, borrowed) from HBP.
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"Ginny and I are meeting for a study session in the library tomorrow. Would you like to join us?"
"Not in the slightest."

They'd just finished up another (great in Hermione's opinion, baffling according to Theo) Ancient Runes lesson, and were spending the fifteen minute break after soaking up some sun in the courtyard.
"Why not?" Hermione asked.
"I don't think I can be around Potter without succumbing to the urge to give him a taste of his own vicious spell."
Hermione fished around in her bag to hide the awkward flush on her cheeks. "Harry isn't going to be there."
"That's immaterial. Ginny's his girlfriend now – she's sold her soul to the devil."
The devil.
Hermione huffed, and popped open a box of butterscotch fudge that her parents had sent her. At once, Theo apprehended the whole lot, and then offered her one.
"You haven't forgotten that Harry and I are still friends, have you?"
"Pshaw. As far as I'm concerned, you're my friend above everything else. I know you'll never say it out loud, but you love me more."
She focused on maintaining the blankest look she could manage... but it didn't matter. He could read her too well. Sure enough, he looked irritatingly pleased with himself.

"I'm going to be busy tomorrow anyway," Theo continued, as the last residues of his smirk faded away, "It's Draco's birthday."
Hermione frowned thoughtfully; "I thought he was opposed to any distractions?"
"Don't care," he replied flippantly, "It's his birthday, and I'm going to ensure that he gets totally shitfaced."

Their conversation was briefly interrupted by the sound of desperate yelling... followed by the source of it: Three Ravenclaw boys tore across the yard as Peeves, who had somehow procured one of Fred and George's Fanged Frisbees, chased after them, cackling maniacally.

After an extended period of munching and sniggering, Theo mused, "By the way... Ginny and Potter... I still can't wrap my head around it."
Hermione turned her eyes heavenwards and said, "It's been like... two weeks, Theo."
He waved off her response, swallowed his fourth piece of fudge, and continued, "It's just so bizarre. So..." he grimaced, "incestuous."
"What!?" She choked on her (still first) piece of fudge.
"It is! It's like she's the closest thing Potter could get to the Weasel-King without being called a poof."
Hermione's jaw dropped, and she stared at Theo for a few gobsmacked seconds.
"That's warped and completely ridiculous," she sputtered, "And don't call Ron that."
"I know you secretly agree with me," he replied pertly, while biting down on piece number five.
"You're an idiot."
He shot her a grave, meaningful look. She narrowed her eyes.
"You're going out with Luna," she reminded him, "Blond hair, grey eyes... was she the closest thing you could get to Malfoy without being called a poof?"
It was Theo's turn to choke then, much to her great satisfaction, and she let that reflect in her tremendously smug smile.
"That's... that's just... Luna's hair is at least four times darker than Draco's!" Theo rebutted in outrage.
"Oh, have an in-depth knowledge of hair colour shades, do you?"
"Shove off, Hermione."
She grinned, "Bet you really regret bringing the word incestuous into play now."
Something that looked frighteningly like determination stole over his face. He studied her with hard eyes, like Perry Mason about to deliver a clincher.
"You know, if I really wanted to date a female Draco, I'd be with you, not Luna."

For a moment, Hermione thought he had actually petrified her, non-verbally. She felt frozen.
"Excuse me?" she demanded indignantly.
Now that he had regained the upper hand, Theo reverted to his leisurely disposition. He picked up yet another bit of fudge and tilted his head serenely.
"Hmm. The same forcefulness... that holier-than-thou conceit..."
Her ears felt like they were on fire. "Shut it, you prat –"
"...that unparalleled wit... the annoying plethora of insecurities... the insane need to prove yourself –"
"How DARE you?!"
"That's exactly what Draco would've said."

Hermione leapt off the banister they were sitting on and stood with her hands on her hips before the insufferable bullshit-spewing, mendacious treat-stealer, glaring in righteous fury.
"You wanker! Give me back my fudge."
"Nope. Has anyone ever told you how resplendent you look when you're having a strop?"
"Theodore, I swear–"
"I'd know though, wouldn't I? As a completely objective party who happens to be on more than familiar terms with the both of you–"
"This is the absolute worst thing you have ever said to me. You take it back. Take it back right now, or else I'll ghhhhfg!"
...Theo stuffed a large piece of fudge right into her raving mouth.
"Doesn't that taste wonderful, Hermione? Nearly as sweet as revenge, is it not?"

Ginny groaned loudly when Hermione set three more books on their already over-crowded table.
"Noooo please! No more! We've been at it for hours and hours!"
"Do I need to remind you that you have your O.W.L.s in two weeks? Look, I know History of Magic can be a little dry –"
"A little? I think Binns' plan is to bore us all to madness and then death so we can all be barmy blathering ghosts like him. Come on Herms... let's call it a day."
"Call me that once more and I'll keep you here all night," Hermione warned, but at Ginny look of superlative panic she relented and said, "Fine. Half an hour more. I will release you once we've gone over the final years of the Giant Wars."

They walked into the common room forty minutes later, with Ginny looking significantly perkier. Ron beckoned them over from a table by the window, while Harry grinned widely, with eyes for Ginny alone. She plonked herself next to him and curled into his side, resting her head on his shoulder.
"Had a productive evening?" Harry asked, smiling into her hair.
"Hermione is a slave driver," Ginny replied around a yawn.
Hermione stuck her nose up in the air, "You'll thank me later. They all come around... eventually... Always. It says a lot about human nature that people haven't made Just Listen to Hermione Without Moaning an adage to live by."
Harry and Ron laughed. Ginny stuck her tongue out, and then unattached herself from Harry just enough to grab a copy of the Daily Prophet that was lying on the floor.
"I'm now going to busy myself with important things like the news, rather than wasting my time mugging up irrelevant facts about wars that happened centuries ago."

If Ginny hadn't been Ginny, and Harry and Ron hadn't been Harry and Ron, Hermione would've loved to take that opportunity to initiate a debate on the merits of historical awareness, and the pivotal role it played in understanding and contextualising the present.
But, alas... they were Ginny, Harry, and Ron. Not that she really knew anyone else who would've been able to give the issue its due consideration.
(Her sub-supersub-subconscious mind whispered a name, and she squashed it down with the force of a sledge hammer.)

"Oi," Ron yelled suddenly, "Don't you berks have better things to do than stare?"
The group of half a dozen odd students that had been standing nearby, staring at Harry and Ginny while giggling and whispering, scattered in different directions; a live demonstration of the process of nuclear fission.
"Damn nosy tossers," Ron grumbled, "I can't believe they're still in a twit about you two."
Harry scratched his nose, looking faintly embarrassed. "Yeah, I'm actually considering keeping the invisibility cloak on for the rest of the year."
"You'd think people had better things to gossip about," Ginny said nonchalantly, "Three dementor attacks in a week, and all Romilda Vane does is ask me if it's true you've got a hippogriff tattooed across your chest."
"What did you tell her?" Harry asked, the edges of his mouth twitching.
"I told her it's a Hungarian Horntail; much more macho."
"Thanks. ...And what did you tell her Ron's got?"
A setup if there ever was one. Both the lovebirds were wearing their impish, conspiratorial grins.
"A Pygmy Puff, but I didn't say where."

Hermione tittered nervously, and Ron's face was like thunder. He pointed a threatening finger at Harry and Ginny, and growled, "Watch it. Just because I've given my permission doesn't mean I can't withdraw it–"
"Your permission," Ginny said with a heightened sneer, "Since when did you give me permission to do anything? Anyway, you said yourself you'd rather it was Harry than Michael or Dean."
"Yeah, I would," Ron admitted stingily. "And just as long as you don't start snogging each other in public–"
Ginny balled up the newspaper in her hand and lobbed it at her brother's head. "You filthy hypocrite! What about you and Lavender, thrashing around like a pair of eels all over the place?"
Harry let out a shocked laugh.

Ron's scowl didn't recede for hours.

Slughorn set them the uncomplicated and tedious task of preparing a muffling draught, and buried himself in a book and an armchair in the corner of the room. That had become his modus operandi ever since Harry had sidled his shameful memory out of him.
Hermione left her asphodel to simmer in diluted syrup of hellebore, and set her chin in her hand, bracing herself for half an hour of idle waiting.

Ten minutes later, Theo shuffled into the room.
"Where have you been for the past two days?" Hermione whispered harshly as he listlessly slid into the stool next to hers.
"Dying," he rasped, rubbing his eyes. He seemed to think that that was an adequate answer to her question.
Hermione arched a brow at him.
"Bleh, alright, I was hungover. Terribly hungover. Near-fatally hungover. A hair's breath away from dying from severe alcohol poisoning."
"I see," Hermione replied loftily, "You celebrated Malfoy's coming of age with great abandon, hmm?"
"Bleh."
"And I suppose he still hasn't recovered? That's why he's missing right now, and why you're sitting here with me?"
"What are we supposed to be brewing?" he asked with evasive faux-curiosity, "Oh... Oh shite... that smells repugnant. I'm begging off today's assignment. Not happening." Theo took the bluegreen scarf (that could now be called a permanent fixture around his neck) and wrapped it around his mouth and nose.
"How much did you drink exactly?" Hermione asked trepidatiously.
"You don't want to know."
"Oh god, Theo."
"Isn't that a bit redundant? 'God' and 'Theo'...? I didn't think you were all that fond of tautology, Hermione," he garbled through the scarf.
She stared blankly at him.
He stared right back, with equally vacant (and bloodshot) eyes.
"Are you saying that you are the supreme, divine creator of the universe and all its creatures, great and small?" she asked.
"Well... yeah. You did say it's called Theology."

Hermione was speechless. She maintained her impassive stare, but something was bubbling in her stomach. It ascended up her chest... her throat...
She threw back her head and laughed.
She squeezed her eyes shut, and basically howled with laughter... and people were probably gawking... and she didn't know why she'd found that so hilarious... but dear... god... she couldn't stop.

She did eventually, though; stop, that is.
Wiping her eyes and gasping, she said, "You're ridiculous."
She didn't dare look around her, knowing that she'd encounter the scandalised stares of a classroom full of people. Her cheeks burned.
A soft chortle from Theo had her glancing up; the scarf had slipped and left his mouth uncovered. He was beaming at her, eyes dancing with amusement, and all the physical signs of his debilitated state had vanished.

Pristine blank parchment laid out in front of her... check.
Inkpot to the right of it... check.
Perfectly sharpened quill in hand... check.
Text by Agrippa... check.
Book of Hebraic numerological translations... check.
Ascribed Arithmancy textbook... check.
Gaelic Methodology... missing.
With a world-weary sigh, Hermione scraped back her chair and disappeared amongst the shelves.

When she returned to her seat, there was a piece of paper sitting on top of her parchment. On it was a very well rendered drawing of a tall, lanky male figure with close-cropped, tightly curled hair, sitting in the pose of Durer's Melancholia. When she looked up, she saw Dean peeping out timidly from behind a bookshelf.
"Sorry," he mouthed.
Hermione blinked, bit her lip, and then nodded once – sharply. He loosened, his shoulders relaxed and he breathed deeply...
With a small grateful smile, he turned around and walked away.

Hermione had struck gold.

After weeks of frustrating fruitlessness, she'd finally found a plausible resolution to Project ETUP (Exhume The Unholy Prince). Clutching an old newspaper clipping in her hand, Hermione stepped in through the Gryffindor portrait hole and made her way towards the corner where Harry and Ron were straining themselves trying to complete their Herbology homework.

Settling on the chair between them, she spoke in her best I-mean-business voice, "I want to talk to you, Harry."
Harry made a small moue at her tone. "What about?"
"The so-called Half-Blood Prince."
"Oh, not again," he cried out in annoyance, "Will you please drop it?"
She squared her shoulders. "I'm not dropping it until you've heard me out. Now, I've been trying to find out a bit about who might make a hobby of inventing dark spells–"
"He didn't make a hobby of it–" Harry cut her off hotly.
"He, he–" she countered, her own temperature rising, "Who says it's a he?"
"We've been through this! Prince, Hermione, Prince!"
"Right!" said ground out. With a bit of a flourish, she slammed the newspaper clipping down on the table before them. "Look at that," she gestured wildly towards it with her hand, "Look at the picture!"

Lifting it up to eye-level, Harry gazed coolly at the picture of Eileen Prince, Captain of the Hogwarts Gobstones Team. Ron leaned over to have a look as well, and immediately his nose scrunched up in distaste; Hermione presumed he was reacting to Eileen's appearance, which, admittedly, defied all criteria of conventional beauty.
"So?" Harry's eyebrows were rising higher and higher as he read the article accompanying the photograph.
"Her name was Eileen Prince," she replied slowly, "Prince, Harry."
He looked up and at her for a long moment, processing what she'd just said. And then... then he burst out laughing.
"No way."
"What?"
"You think she was the Half-Blood...? Oh, come on." Harry, still chortling, placed the paper back down on the table dismissively.
"Well, why not? Harry, there aren't any real princes in the Wizarding world! It's either a nickname, a made-up title somebody's given themselves, or it could be their actual name, couldn't it?" Harry snorted, and she gnashed her teeth, "No, listen! If, say, her father was a wizard whose surname was Prince, and her mother was a Muggle, then that would make her a 'half-blood Prince'!"
"Yeah, very ingenious, Hermione..."
Surely, surely, there was steam coming out of her ears. "But it would! Maybe she was proud of being half a Prince!"
"Listen, Hermione, I can tell it's not a girl. I can just tell."

Oh. Oh. So she was up against some transcendental bond of brotherhood here. Harry's lad-radar had sounded off – he could just tell.
"The truth is that you don't think a girl would have been clever enough."
"How can I have hung round with you for five years and not think girls are clever?" he said witheringly, "It's the way he writes, I just know the Prince was a bloke, I can tell. This girl hasn't got anything to do with it. Where did you get this anyway?"
"The library," she replied, ignoring the way he rolled his eyes, "There's a whole collection of old Prophets up there. Well, I'm going to find out more about Eileen Prince if I can."
"Enjoy yourself," Harry grouched.
"I will," she snapped, "And the first place I'll look is records of old Potions awards!"
She left quickly, not allowing him the opportunity to snark at her any further.

On reaching the library, she put together a teetering pile of old records and newspapers –– and then stopped dead (almost spilling paper everywhere) when she got to her usual table.
"Sweet Dagda!" Seamus exclaimed the moment he saw her, "Hermione... you're here! Fantastic," he promptly stood up and began packing his things, "You can take over – I'm officially off duty now. Fucking finally. I'm leaving. I'm off. Slán."

Hermione turned to the two remainders.
"Theo, Luna, hi. Er... what's going on?"
"Well, Finnigan kindly agreed to sit here so that it wouldn't be just the two of us. No need to set the rumour mills going, you know," Theo replied with an easy smile.
"Ah." Hermione took the seat Seamus has just vacated before tentatively asking, "You asked Seamus to be your cover? Of all people...?"
Theo shrugged, "He's a laugh. I like him."
"Seamus. You like Seamus."
"Yeah. You know, Hermione... I don't know why you force yourself to hang around with Potter and Weasley when you have him around."
Before she could retort, Luna chimed in, "Harry's perfectly lovely."
Aghast, Theo gaped at her in betrayal so she clarified, "Yes, he does unpleasant things sometimes, but I don't think that's him, really. I think there's something foreign and insidious in his head that's messing him up... I see it in his expression sometimes," she lowered her head gravely, "Probably an army of malicious wrackspurts."
"Love," Theo said disdainfully, "You know I think you're the most intuitive and perceptive witch in the world, but if you start defending Potter, I'm going to get terribly mardy."
Luna smiled seraphically; "That's alright. I know how to cheer you up."
A grin, a leer, and a purred, "That you do..." from Theo had Hermione snapping her fingers twice in warning.
"Reign in it, you two. I may have agreed to be your scapegoat, but I did not agree to a peepshow."
"Oh, shut up," said Theo.
"I suppose we won't be inviting you to celebrate Beltane with us next year," said Luna.
A statement of finality if ever there was one.
They each fell into their own work (though Hermione suspected that Theo and Luna were holding hands under the table) and sat in uninterrupted silence for a long while.

Hermione's mouth was thinned in annoyance. Eileen Prince hadn't been awarded a single prize of academic excellence. It appeared that her only claim to fame was being a competent gobstones player.
She poured over Prophet after Prophet, and found nothing remotely useful. Desperate, she even skimmed through papers from years later. Nothing in the minor accomplishments pages. No mention in the Page Three high society drivel. In the wedding announcements pages...
Oh fuck.

The engagement is announced between Eileen, daughter of Reginald and Eimear Prince of Ballycastle, and Tobias, son of Abner and Rachel Snape of Cokeworth, England.

She scrambled through the remaining Prophets, hunting, hunting...

On 9th January, 1960, to Eileen (nee Prince) and Tobias Snape, a son, Severus Snape.

"Oh fuck," Hermione groaned out loud.
Somewhere in the background, a voice that sounded like Theo's asked, "What is it?"
Hermione ignored the voice.
Severus Snape was the Half-Blood Prince. It made sense – it made complete sense. He had known how to counter the Sectumsempra curse... immediately asked to see Harry's potion's book... And, well, there was no denying that he was exceedingly clever... a dab hand at potions...
She stood up, sending the prophets back in place with a careless wave of her hand.
"I'm sorry," she rushed, "I have to go."
"Oi. Hey... Hey," Theo caught hold of her wrist, "What's going on?"
"Nothing," Hermione stated firmly, "I just need to speak to Harry. Don't worry, I promise it's nothing serious..."
"You look spooked," Luna added, "Something has rattled you. But she doesn't want to tell us, Theo. You should let her go."
He did not relent. "Hermione–" he frowned up at her, then at Luna, and then back at her, "Ugh, fine. Go. But you will tell me what this is about yeah? Later?"
He released her wrist, and she nodded, and without delay tore out of the library. Her footfalls thumped loudly against the stone floor; if there was any piece of information that could convince Harry to give up the book... this was it.

When she finally stumbled into the common room, Ron was sitting alone and Harry was nowhere in sight. She raced over to him and panted, "Where's Harry?"
He looked at her with anxious eyes. "Dumbledore sent for him. He's been gone a while now..."
All thoughts of Snapes and Princes evaporated right out of Hermione's mind. She gasped. "You... you don't think he's found..."
"Donno," he muttered, rubbing his hands together uneasily.

Yet again, Hermione and Ron were left to stew in worry and disquiet, wondering what had become of their friend.

Countless minutes later, Harry could be seen running across the room. Hermione shot up to her feet; "What does he want? Harry, are you okay?" she demanded fretfully.
"I'm fine," Harry called over his shoulder, as he dashed up the stairs and disappeared into his dormitory. She sat back down robotically and exchanged a startled look with Ron...
...and then Harry was back, carrying a variety of indistinguishable things in his hands.

"I've got to be quick," he wheezed, dropping down onto his haunches in front of them, "Dumbledore thinks I'm getting my Invisibility Cloak. Listen... he's found a horcrux –" Hermione and Ron both gasped, but Harry paid no heed to their amazement, "I'm going with him to get it–"
"Where–" Ron began.
"It's hidden in a cave on some distant coast... the cave in which Riddle once terrorised two children from his orphanage –"
"But what about –"
"I don't have time to get into the fucking details! I ran into Trelawney on the way... she was trying to get into the Room of Requirement, but was thrown out by somebody already in there. Somebody who was whooping triumphantly. So you see what this means? Dumbledore won't be here tonight, so Malfoy's going to have another clear shot at whatever he's up to."
Hermione opened her mouth, but Harry foresaw her interjection. "No, listen to me!" he growled furiously, "I know it was Malfoy celebrating. Here–" He thrust something into Hermione's hands... an old, yellowed bit of parchment: the Marauder's Map, she realised.
"You've got to watch him and you've got to watch that bastard Snape too," Harry continued frantically, "Use anyone else who you can rustle up from the D.A.; Hermione, those contact Galleons will still work, right? Dumbledore says he's put extra protection in the school, but if Snape's involved, he'll know what Dumbledore's protection is, and how to avoid it – but he won't be expecting you lot to be on the watch, will he?"
"Harry–" she tried again, her voice shook with tension.
"I haven't got time to argue," said Harry tersely. "Take this as well–" He dropped a pair of socks onto Ron's lap.
Ron stared down at them. "Thanks. Er – why do I need socks?"
"You need what's wrapped in them... it's the Felix Felicis. Share it between yourselves and Ginny too. Say good-bye to her for me. I'd better go, Dumbledore's waiting–"
Ron extracted the tiny bottle, and Hermione jumped to the edge of her seat, "No!" she half-yelled, "We don't want it. You take it. Who knows what you're going to be facing?"
"I'll be fine; I'll be with Dumbledore," said Harry with a shake of his head, "I want to know you lot are okay… Don't look at me like that, Hermione, I'll see you later…"

And suddenly, he was a blur, dodging the students milling about the common room, before finally vanishing from sight.

"Bloody fucking hell," Ron breathed.