Disclaimer: I do not own Harry Potter; J.K. Rowling does.

Author's Notes: This story makes use of that venerable cliché, accidental travel into a parallel world or alternate universe. A good many of the characters will be OoC as compared to their canon versions, and the timelines of the two worlds do not match up exactly. As this story parts ways with Harry Potter canon somewhere during Chapter 9 of Half-Blood Prince, anything introduced after that point may not be in this story, and, even if it is, may appear very differently.

There will be around 30 chapters, of which 8 are already written. At present I am intending to add a new chapter every 2-3 weeks. This may or may not be a sustainable update schedule. Time will tell.

Alternate History

1. When I See Stars

Hermione had given up trying to convince them that she was right, even though she knew that she was. What did it matter that Professor Snape was going to be teaching Defence this year? He could hardly be any worse at it than most of the other teachers they'd had. Really, compared to Umbridge, she was willing to bet that he would seem like an excellent – maybe even a fair – teacher. And he wasn't going to teach them Dark curses, or use them for experiments, or whatever it was that Harry and Ron were afraid of. How they thought that he would get away with anything of the kind while under the watchful eye of Professor Dumbledore was beyond her. No; it was quite apparent that, as usual, they simply weren't thinking at all.

As they walked along the first floor corridor towards the Defence classroom, she couldn't resist making one last appeal for sanity, for all that she knew that it probably wouldn't do any good. "Honestly, what on earth do you imagine he's going to do to us? Everything is going to be fine. Much better than lessons with Professor Umbridge, or... or Lockhart." She blushed just a little, remembering how silly she had been in her second year. Silly about a man, too! That was not like Hermione, not in the least. Harry and Ron exchanged a look and gave matching quiet laughs, while she sighed and shook her head. "Anyway, trust me; the world isn't going to end just because Professor Snape is teaching Defence now. You'll see."

Later on, Hermione would remember those words and wonder if the universe had a sense of humour.

The lesson got off to an inauspicious start when the Professor snapped at them to keep their textbooks in their bags, lectured them for five minutes straight, and then demanded that they all demonstrate their duelling skills. Hermione's heart sank; she knew her strengths, and she also knew that practical Defence was not one of them. It wasn't the spells themselves – as usual, she had managed to learn all of the magic involved remarkably quickly – it was simply that she had slow reflexes, and tended to freeze up in tense situations. That was why she always tried to be prepared for everything. But, as Professor Snape would no doubt delight in reminding her, poor duelling skills were not an option for one of Harry Potter's best friends. She needed to improve, and she knew it.

And she tried to apply herself during the mock-duel, she really did – her close call with Dolohov at the Ministry was never very far from her mind – but it was very difficult. Especially since her partner for the exercise was Lavender Brown, who seemed more interested in making sheep's eyes at Ron than in paying any attention to what she was doing. Hermione scowled at her oblivious opponent. I wish you joy of him. Heaven knows, I've spent long enough trying to get him to notice me, but he never has.

Then she realised that she was daydreaming – and about a boy, of all things – in the middle of a lesson, and she struggled to bring her mind back to the task at hand. Before she could collect herself sufficiently, an irritated Professor Snape bore down upon the hapless pair and favoured them with a poisonous glare. He sneered. "Miss Granger, Miss Brown, you are supposed to be duelling. Kindly do so immediately, or you will both find yourselves practising in detention tonight."

The threat of getting a detention before the end of the first week of term had an electrifying effect on both girls, and they rather hurriedly started to throw hexes at each other. It was almost like being in the DA again – or would be, if she could somehow ignore the highly critical Professor who was watching her every move. Hermione refused to let his scrutiny bother her, though she did try to cast a few spells non-verbally just to show that she'd been listening to the lecture – but of course, her effort was to no avail. She'd learned a long time ago that Professor Snape would never admit to being impressed by her work, no matter how well she managed to do.

She sighed – there was no point in sulking about how unfair everything was – and concentrated on dodging and deflecting the poorly-aimed spells that Lavender sent her way. Had it not been a practice, and had she not been so determined to cast non-verbally, Hermione would have won very quickly; she might not have been a very good duellist, but at least she was concentrating. Around them, other pairs fought with more flashy – and more accurate – spells, but her attention was fixed entirely on Lavender. It was just a classroom exercise; there was no reason to care what anyone else was doing.

That sort of attitude was all very well, but it did mean that she never saw what hit her.

One of Lavender's spells was on target for once, and Hermione actually succeeded in countering it with a non-verbal Protego – and then something very strange happened. There were, inevitably, a number of stray spells flying across the room, and as Lavender's spell ricocheted off the shield, it collided with one of these. The impact between the two was loud and violent, an explosion of varicoloured light. A spike of near-deafening sound reverberated painfully through Hermione's head, leaving her dazed even as the rush of expanding air knocked her to the ground.

Her vision blurred for a moment, and black spots danced ominously before her eyes – but she took deep calming breaths and somehow managed not to lose consciousness. Not wanting to cause a scene, she tried to stand up... which proved to be a mistake. The room swam out of focus again, and her legs refused to straighten under her properly, so she collapsed back to the floor with an indignant huff. Of all the places to have an accident like this, why did it have to be here, under the cruel and unsympathetic eyes of –

"Miss Granger! Are you alright?"

Professor Snape?

Sure enough, it was Professor Snape's voice – but it didn't sound quite right. There was some emotion there that didn't belong. After a few seconds, Hermione's sluggish mind realised what it was. Concern. As strange as it sounded, Professor Snape was worried about her. Was she dying, then? Panic rose up in her chest. Surely he would only sound quite so afraid for her wellbeing if she were actually at Death's door? She didn't feel that bad – only weak and a bit dizzy – but maybe he knew something she didn't.

Once again she struggled to get up, and once again she was forced to admit defeat. "My head," she murmured, clutching at the floor and hoping that the room would stop spinning soon.

And then, bizarrely, Professor Snape was standing right before her, looking down at her with an expression she couldn't quite make out. "Miss Granger, did you hit your head when you fell?" He didn't shout at her. He didn't take any points from Gryffindor. She couldn't understand it.

Hermione blinked a few times. "I... don't know. Maybe?" She wasn't physically injured. Aside from her trembling, uncooperative limbs, there didn't seem to be much wrong with her at all. So why was Professor Snape so upset? Perhaps this was how teachers were supposed to react to an accident in their class, but she'd never seen any teacher at Hogwarts – let alone Snape – actually do it.

"Look at me." Crisp efficiency had replaced the usual sneering disdain in the Professor's voice, and Hermione found herself meeting his eyes more out of surprise than anything else. Was it her imagination, or was there more warmth there than she'd expected to find? She couldn't focus on him; her mind was in a whirl. Something is wrong here. A shiver ran down her spine, but she wasn't cold. Snape spoke again, in a gentle voice that she'd never heard from him before. "You need to see Madam Pomfrey." He turned back towards the class and barked, "Mr. Potter, Mr. Weasley – escort Miss Granger to the hospital wing and come straight back, do you understand?"

Two other shapes moved towards her; she squinted up at them and saw that it was Harry and Ron. Or, at least, it looked like them. She wasn't sure if these people really were her best friends – because, if Snape had seemed too concerned about her plight, her two boys didn't look as though they cared at all. While they did help her to her feet, and support her as she walked towards the door, they didn't say a word to her, or even so much as look at her. Yes, something is very wrong indeed. Cold tendrils of fear coiled around her heart. What was going on?

As she was about to leave the room, Hermione heard Professor Snape clear his throat. She looked back and met his eyes once more – and this time she couldn't look away. His lips didn't move, but she heard his voice as clear as day nonetheless: "Don't say anything to them." Then he dropped his gaze, and suddenly she could move again. She stumbled out into the corridor, her heartbeat echoing in her ears. Snape had spoken to her inside her mind, warning her against Harry and Ron. But how had he done that? And why would he do that? It didn't make sense; nothing did. If only she could believe that this was nothing more than the result of a head injury!

Awkwardly, without looking at the boys who should have been her friends, Hermione said, "Thanks for helping me." She felt fairly confident that Professor Snape hadn't meant that she should be completely silent, only that she should be careful with her words.

"The Professor told us to." Harry's voice sounded gruffer and harsher than it usually did.

His obvious indifference to her made Hermione want to cry. "Yes, well, thank you anyway," she said, remembering her mother's lectures on good manners.

Ron snorted. "Gryffindors," he said, with every sign of great disdain.

Shocked, Hermione blurted out: "But you–" And then she stopped herself. Snape's warning echoed in her memory, reproaching her. Don't say anything to them. "Never mind."

"No, please go on, Granger – I am so curious as to what you were going to say about us." The sound of her surname on Harry's lips stunned her into horrified silence. This was all wrong. This wasn't Harry. It couldn't be Harry. Her best friend didn't talk that way – not to her, not to anybody save perhaps Malfoy. Even worse, there was a sardonic cast to his features that made him look quite unlike his normal self. This has to be a dream. A terrible nightmare. Tears pricked the corners of her eyes, and she trembled miserably.

Even though he was all wrong too, Hermione was still glad when Ron interrupted. "Leave it out, Harry. It's not right to start having a go at a girl while you're taking her to the hospital wing." He didn't seem to have any sort of special concern for her, but it did comfort her at least a little to think that Ron was still a decent person, whatever else was wrong with the world.

Harry scowled. "I wasn't having a go at her," he protested, an unfamiliar note of petulance and nasal whine in his voice. Ron glared wordlessly at him and he subsided, though not without grumbling resentfully and pulling an unpleasant face at his friend. They walked the rest of the way to the infirmary in silence, which came as a blessed relief to Hermione. As strange and unsettling as it was to be with her boys and not say anything to them, it was far better than trying to make conversation only to be reminded that they weren't behaving like her boys at all.

If this is a dream, how do I wake up?

Once they reached the hospital wing, she found that Madam Pomfrey was exactly the same as ever. The nurse hurried over to them, all concern and eagerness, ready to help – and for just a moment, Hermione could almost let herself believe that everything was normal. Almost.

"Miss Granger? What's wrong? What happened?"

Hermione had to suppress a hysterical laugh. I wish I knew. "I... um, well, I was in Defence..."

"She just collapsed." Harry cut in. "I don't know why. Snape told us to bring her to you – maybe you can work it out." He shrugged and nudged Ron. "C'mon, Weasley, we'd better get back to class."

"Right you are, mate." He looked like Ron. He sounded like Ron. As far as any of her senses could tell, he was Ron. And yet he couldn't be, because Ron wouldn't leave her in the infirmary with barely a nod of acknowledgement, not even if he were really angry with her. Nor would Harry follow him without a word, without any sign of affection whatsoever – no matter what Snape had said about returning to class. Everything was wrong. Harry and Ron were wrong. Hell, they weren't even Gryffindors anymore by the sound of it. And, well, she supposed that everything else might have a rational explanation – but not that. That had Hermione completely at a loss.

"Now, Miss Granger, how are you feeling?" At least one person was acting normally; Madam Pomfrey would never be deterred from seeing to a patient's wellbeing. Hermione smiled weakly.

"A bit dizzy still," she admitted. "And wobbly."

"You ought to have said so at once," Madam Pomfrey said, reproachfully. She firmly escorted Hermione to the nearest bed, and all but forced her to sit down, shaking her head disapprovingly. "That's better. The last thing I need is patients injuring themselves further in my infirmary. Now, tell me exactly what happened during your class."

"I – I'm not sure. I don't remember fainting or anything like that. Somehow I was on the floor, I couldn't focus my eyes properly, and when I tried to stand up, I couldn't do it." Hermione took a deep breath to steady her nerves. "Really, though, I can't remember anything. I think that's why Professor Snape was worried – he asked if I'd hit my head. Maybe I did; it'd explain why I feel so confused." She wasn't sure how much she should say; the mediwitch couldn't do much to help her if she didn't give all the details. But, on the other hand, she didn't want to give the impression that she was insane. Maybe I am insane. "I mean – well – nothing feels quite right."

"Are you in any pain?" Madam Pomfrey seemed suddenly much more alert, and Hermione cursed inwardly. Apparently her vague allusion to the problem was more than enough to worry the nurse – although she doubted that even the most assiduous medical attendant would ever suspect exactly what she meant. Fifteen minutes ago, the world was a different place. How was Madam Pomfrey supposed to fix that? How was anyone?

"No, there isn't any pain. I just... I feel fuzzy-headed. Like I've forgotten things I ought to know." Hermione shook her head and winced slightly. "And it's strange to be told that I collapsed for no reason. I don't know – I'm scared."

Madam Pomfrey gave her a thin-lipped smile of sympathy. "Yes, dear, I imagine you would be." She clucked her tongue soothingly. "Not knowing what's wrong with you is never easy for a patient, though some bear with it more calmly than others. Now, then – have you been eating and drinking normally during the holidays? Or have you been missing meals and staying up late to spend more time on your homework?" There was a dry note to the nurse's voice that made Hermione feel a little ashamed of herself, even though she hadn't skipped a meal since her third year.

"I think I've been doing everything more or less normally," she said, slowly. "Or, at least, I don't remember having done anything that might cause me to collapse in the middle of the day." But then, she did remember a lot of things that apparently had never happened, so what good was her memory really, when all was said and done?

"Hmm." Madam Pomfrey looked thoughtful for a moment, and then waved her wand over Hermione in a complicated pattern. After a brief pause, a pale blue light appeared; it hung in mid-air for about ten seconds before vanishing. "Well, it looks like you're not pregnant, at least," the mediwitch said, in a brisk and professional voice.

Hermione froze, part embarrassed and part indignant. "I beg your pardon?" Why would anyone even bother to test her for that? Wasn't it obvious that she'd never jeopardise her studies in such a way?

Maybe it wasn't, though, because Madam Pomfrey laughed. "Oh, my dear," she said, gently. "You're a sixteen-year-old girl, and you nearly passed out during a not particularly taxing lesson. It seemed like a good idea to rule that out first." She raised an eyebrow. "And don't you give me anything about your reputation, either, young lady. I've worked at this school for decades – I know teenagers, and I know well enough that the quiet bookworms are in no way immune to such temptations, whatever the teachers might want to think." Pomfrey sighed and then went on, "Be that as it may, you're all clear there. It would have explained the situation quite handily, of course – but never mind that now."

She still felt rather affronted, but Hermione knew that the mediwitch had to do her job, which was to figure out what was wrong. Doubt gnawed at her, whispered that there was no way this could even be figured out, let alone cured, but she forced the thoughts away and tried to sit as still as possible. Madam Pomfrey cast a number of unfamiliar spells over her, and magical lights flared over the bed, changing colour in a way that meant nothing to Hermione but hopefully told the nurse something useful. This went on for some minutes, and by the end she couldn't help but start to fidget and worry.

After the spells stopped, Madam Pomfrey made a number of notes on a piece of parchment, and then turned back to Hermione. "Well, Miss Granger, I'm happy to say that I can't find anything wrong with you at all. The level of magical residue on your person is a little high, true, but it's still within normal bounds. In fact, you seem to be perfectly healthy." She smiled at Hermione's perplexed expression. "I know that makes it rather puzzling that you should have collapsed – but, on the bright side, at least it doesn't appear to be a symptom of a serious underlying problem."

"I – yes, I suppose you're right." Hermione was honestly rather disappointed. She'd hoped that there would be something physically wrong, something that would explain what had happened to her. Why Professor Snape suddenly cared if she was injured, and why Harry and Ron did not. Why she knew that she'd been hit by spells in a classroom duel, but had apparently collapsed for no reason in the middle of a completely different Defence lesson. But then, was there any sensible, rational way to account for those things? Her head spun and her thoughts were muddled.

"But your inquiring mind would prefer to find a proper solution, I'm sure," Madam Pomfrey said, shrewdly. Hermione, startled, looked up at her and let out a strangled snort. It sounded rather silly when put like that. "I understand the feeling, dear – it was part of why I went into medimagic in the first place – but after all these years I've come to realise that you shouldn't complain if someone turns out to be unexpectedly healthy." She smiled. "How do you feel now? Has the dizziness passed?"

Hermione shrugged and tried to stand up. The blood seemed to rush to her head, and she swayed slightly. "No, I don't think so. But – you said there was nothing wrong with me?"

Madam Pomfrey patted her gently on the shoulder. "There is nothing wrong with you that I can detect. It's likely that either you aren't getting enough sleep or you're dehydrated. Neither of those things would show up on a health scan, but would make you feel weak." The nurse poured out a glass of water and handed it to Hermione. "My suggestion is that you drink this and then lay down here for a little while. It should pass soon enough, and you'll be right back to normal." She gave Hermione a rather stern look, and said, "And no pretending to have recovered so that you don't have to miss any classes, either." Her eyes flashed with amusement, and she added, "I don't often have to say that."

"That doesn't surprise me." Hermione had seen her classmates' attitude to lessons. It was not one that she had ever shared, though in the present circumstances she did feel unusually reluctant to go back to her lessons. She still didn't know what was going on; she'd hoped that the medical examination would help, but all it had told her was that she wasn't sick or injured. Or not only that – if she'd been under the effects of a malicious spell, she imagined that Madam Pomfrey would have been able to tell. Maybe eliminating possibilities was useful, but she wished she could get a concrete answer. She sighed. "I'm sure I'll feel better in no time," she said, with more optimism than she felt.

"I'll leave you in peace to rest," Madam Pomfrey said, turning back the covers on the bed Hermione was sitting on. "You don't have to sleep, but it might help. And do make sure you drink that water." So saying, the nurse gathered up her papers and bustled across the hospital wing towards her private office. Hermione watched her go, and then shrugged and reached for the water. She'd always been told to respect doctors and follow their advice, so she obediently drained the glass, took off her outer robes, and lay down on the bed. There were far too many thoughts in her head for her to be able to sleep, but she did gradually begin to relax and let her eyes drift closed.

She ought to have known that the peace and solitude couldn't last. Hermione wasn't sure how long she had been lying there when she became aware of the fact that she wasn't alone in the room anymore, but it hadn't been long enough. She didn't want to see anyone or go outside the hospital wing until the world had decided to go back to normal. Whoever had come to visit her would just have to go away, because she wasn't in any mood to talk to them.

"Miss Granger." Of course, it would be a teacher. Hermione couldn't ignore a teacher; she wasn't made that way. She stretched a little and then sat up to look at her visitor. Professor Snape stood a few feet away from her bed, holding her schoolbag in one hand. "You left this in my classroom," he said, although the explanation wasn't really necessary. Perhaps Hermione was imagining things, but he seemed almost nervous, which wasn't like Professor Snape at all. "I could have asked Potter or Weasley to take it when they escorted you, but I must confess that I wanted the opportunity to talk to you privately."

It was suddenly very difficult to breathe. "Did you, sir? I – what did you want to talk to me about?"

Professor Snape didn't answer immediately. He looked at her carefully, as though she were a puzzle he was trying to solve, and then the most incredible thing happened – he smiled. "I'll get to that shortly. It would be remiss of me not to ask you if you are feeling any better."

Still wary, Hermione said only, "Yes, sir, quite a bit better." She thought for a moment, and then added, "Madam Pomfrey says there's nothing physically wrong with me."

"Well, that is something of a relief," Professor Snape replied, and it seemed as if he meant it. He put her bag down on the floor and sat in the chair next to her bed. Leaning forwards a little, he said, "Don't spread this story around too much, but I was worried about you."

Hermione was stunned. "Who are you and what have you done to Professor Snape?" She knew that it wasn't the wisest thing to say, but she couldn't help herself.

He actually laughed. Hermione stared. Much as she wouldn't allow her boys to speak ill of the Professor in her hearing, she was still slightly surprised to find him look so... human. It didn't last long; he quickly sobered and said, "That is the issue, isn't it, Miss Granger?"

"What – what do you mean?" Hermione was flustered, and she had quite forgotten to call him 'sir', but she couldn't deal with the situation becoming any stranger than it already was.

"After you fell in my classroom, I saw the way you looked at me. I could tell you were confused by the way I was behaving – as you are now – and I think I know why."

Her first thought was that he couldn't know anything, not just from looking into her eyes. Then she remembered hearing his voice in her mind, and it all made sense. There was an explanation; it just wasn't the one he was giving her. After the morning she'd had, this realisation actually made her angry – even if he was a teacher. In a flat, cold voice, Hermione said, "You used Legilimency on me."