Author's Notes: A big thank you to FreeDaChickens at Perfect Imagination for looking over this chapter. All remaining errors are my own.

4

MDIU.

Harry mused over the letters as he showered that morning, as he dressed, as he packed his schoolbooks into his bag, and as he made his way down to common room. Hermione was standing near the bottom of the stairs with Ron, and both of them seemed reluctant to approach him.

'Are you coming to breakfast?' Harry asked, looking from one to the other in confusion.

'Erm – okay,' Hermione said nervously. She moved swiftly towards the portrait hole and opened it to usher Ron though to the other side. When Harry stepped past her she stopped him with a hand on his elbow.

'You're ... you're feeling all right now? Everything's okay?' she said quietly.

Memories of yesterday flashed briefly through his mind: the visions, the screaming, the vomit, Hermione's fearful concern as she sat him down. It must have been quite an ordeal for her, Harry realized. The way he had behaved yesterday, it was no wonder his friend was worried.

'I'm fine,' he said now, 'really. I'm sorry about ... y'know.'

Hermione nodded and then smiled, though the smile seemed rather forced. 'I'm just glad you're feeling better. It's fine.'

They made their way down to the Great Hall in silence and settled at the breakfast table. Harry tried not to watch as Ron piled his plate with sausages, the sight of it making him queasy. The fact of the matter was that he was not fine. The visions seemed to have gone, but their effects persisted in the tightness of his chest and the sweatiness of his palms. His head ached, and a lingering sense of fear stalked his thoughts like a shadow.

He sipped his pumpkin juice and cast his mind back to the previous night's dream. That it meant something was beyond doubt to Harry; the little he could remember of it clawed at him with urgency. There had been a quest, he thought, a journey to uncover a secret ... and the meaning of those letters, MDIU, would help guide him on his way...

Hermione cleared her throat and set her spoon down. She met Harry's eyes, then looked past him to the far side of the hall.

'Malfoy seems better today,' she said. 'Don't you think, Harry?'

Harry stared at her. 'Malfoy?' What did he have to do with anything? 'I don't know.'

He turned around in his chair to glance over at the far table. Sure enough, Malfoy looked brighter than he had the last time Harry had run into him. His cheeks had more colour, and though he was sitting apart from the other Slytherins, he seemed cheerful enough.

Harry turned back to Hermione, shrugging. 'S'pose,' he answered. He really wasn't interested in the wellbeing of Malfoy of all people.

Ron seemed to share Harry's view. 'What are you worried about that git for, Hermione? Who cares how he is?'

'I just thought Harry might, that's all.'

Ron shot her a look of bewilderment that mirrored how Harry felt. 'Why would Harry care?' he said.

Harry said nothing. The only time he had spoken to Malfoy this term, the only time he had so much as noticed him, was during his search for the Resurrection Stone in the forest two nights ago. Hermione could not know about that – though hadn't she hinted about it before?

Harry patted his pocket, feeling for the stone. It was still there, still safe – still useless, he thought dejectedly. But there was no way Hermione could know about it.

Harry changed the subject before he could think better of it.

'MDIU,' he said. 'Does it mean anything to either of you? Is it an acronym or something?'

A short, puzzled pause met his words, and then Hermione launched straight into this new topic, clearly unable to leave a question of any sort unanswered.

'I don't know...' Her eyebrows were furrowed. 'It does sound like an initialism, but I can't say I've heard of it. Where did you read it? What's the context?'

'I'm not sure,' said Harry. Though he couldn't remember the details of the dream, it was still too private to share. 'They said it on the wireless,' he found himself saying. 'I was half-asleep, so I don't really remember what it was about.' He paused, his mind trying to grasp at the imprint the dream had left. 'I think it might have been ... something historical.'

'"Something historical",' Ron repeated. 'Well, that narrows it down.'

Harry frowned, knowing that Ron had a point. The letters in his head could stand for anything or nothing at all. If Hermione couldn't identify them, then how was he supposed to?

'I'm going to the library,' he decided, and he pushed himself up from the table. He staggered a little as he stood.

Ron caught his arm. 'Don't you think you should eat something, mate? Then get some rest? We've got a whole hour free before Charms.'

'I'm fine,' said Harry. He extricated himself from Ron and turned his back on his friends before they could even begin to argue.

When he reached the library, he made a beeline towards the biggest dictionary he could find and pulled it down to rifle through it. 'MDIU' was absent, the nearest entry being 'Mdme.' Harry sighed and heaved the dictionary back onto the shelf. He scanned the spines of the other reference books and found dictionaries of potions, of arithmancy, of charms and of Quidditch slang, but none of only acronyms.

Sighing, he sat down at the nearest table and tried to gather his thoughts. He could ask Madam Pince, but he didn't feel it was safe. For all Harry knew, MDIU might have darker connotations than Sectumsempra, so confiding in the librarian would be too risky. She might ask questions, and there was no guarantee that she would point in him the right direction even if she was able.

Approaching fellow students was a safer bet, but since neither Ron nor Hermione could help him, it probably wasn't knowledge learnt from either pureblood upbringing or books.

Having swiftly run out of ideas, Harry pulled a piece of parchment from his schoolbag and scribbled the letters down with his quill.

M-D-I-U.

Nothing jumped out at him, so he switched the letters around to see if meaning might emerge.

U-I-D-M.

He carried on moving the placement of each letter until twenty-four unique permutations ran down the parchment. None of them struck him with familiarity; each seemed as meaningless as the last. With no better options, though, he decided to check for certain. After heaving the dictionary back off its shelf, he looked up each of the combinations in turn.

He was up to 'DMIU' – having had no luck so far – when an interruption announced itself in the form of Neville Longbottom.

Harry looked up as his Gryffindor roommate cleared his throat.

'Sorry, Harry.' He sounded it. 'Everywhere else is taken, do you mind?'

Rather than wait for a reply, Neville dropped into the chair furthest from Harry and turned away from him.

It occurred to Harry, as he watched Neville dig out an old Herbology book and dump it on the table, that these were the first words that had passed between them since term had started. Certainly Harry had not gone out of his way to speak to Neville, but his housemates hadn't tried to talk to him either. In fact now that he remembered it, Neville had blanked Harry in the Great Hall the other day when he had been sitting with Ginny.

A smile broke out across his face as he remembered his sixth year and how desperate he had been to avoid Dean when he fell for the redhead. Was it possible that Neville was now going through something similar? The two of them had seemed very close at the feast...

The more he thought about it, the more certain he was that this was the case. Harry knew he ought to say something to Neville – ought to explain that he and Ginny had separated amicably, that he did not mind if she had moved on – but the thought of speaking so openly about relationships did not appeal. Still, he ought to say something to show there were no hard feelings...

'Hey Neville,' said Harry now. He waited as his friend turned nervously towards him and then gave him a reassuring smile. 'Are you busy? I could really do with your help on something. It's a long shot, but I'd really appreciate your input.'

And when his friend motioned for him to continue, though reluctantly at first, Harry moved into the seat next to Neville and explained about MDIU.

The lack of progress they made did not matter terribly to Harry, who had not expected Neville to have heard of MDIU and therefore saw no reason to be disappointed. Though the pair of them didn't find any dictionary entries for any of the combinations, Harry found it comforting to work alongside a friend who asked no questions. So comforting, in fact, that he found himself sharing more with Neville than he had with either Ron or Hermione. He did not go into great detail, but he admitted that the letters had come to him in a dream.

They parted at the end of the hour, Neville on his way to Herbology, Harry to Charms.

'Quidditch tryouts on Saturday,' said Ron by way of greeting as Harry took the seat next to him in Flitwick's classroom. 'Demelza's put a notice up.'

'Oh,' said Harry. He thought back to yesterday's meeting in Petrova's office. 'I don't think I'm going to bother.' Then he remembered the feast in the Great Hall the evening before. 'We should go and see Hagrid though. Today after classes.'

'You're joking!' said Ron. He winced at an elbow in the ribs from Hermione, who was sitting on Ron's other side. Professor Flitwick was staring at them pointedly.

'If you're all quite ready,' squeaked Flitwick from his perch on the teacher's desk, 'today we will be practicing Imperturbable Charms.'

There was no time to speak as students spelled the desks to one side and Flitwick conjured several dinner plates to hang static in the air around them. The aim of the lesson, he explained, was to cast the charm on their plate strongly enough that no object could break through the barrier to shatter it.

'You'll also get some practice at Protego, no doubt,' he finished.

Two minutes into the chaos, Harry saw what Flitwick meant: he was shielding himself left, right and centre from flying shards of porcelain. Other students less experienced with the charm had to resort to different means of defence. Harry tried not to laugh as he watched Seamus duck and cover.

'So why no Quidditch?' shouted Ron above the din of breaking crockery. 'You can't be serious about not wanting to play.'

'Give it a rest, Ron,' said Hermione. She flicked her wrist and sent a book flying towards her dinner plate. It stopped mid-air a centimetre away and dropped unceremoniously to the floor. Smiling to herself, Hermione Accioed the book and raised her eyebrows. 'He's got more important things to do than play Quidditch, haven't you, Harry?'

Harry flung a Sickle towards his plate and frowned when it shattered. He cast an apologetic look at Ron. 'I just need to concentrate on schoolwork; I'm so out of touch at the minute.'

'So am I!' Ron pointed to his own recently broken plate in illustration. 'But it's Quidditch, you don't just give up Quidditch, Harry! Quidditch!'

'I said I'm not interested, all right! Stop saying "Quidditch"!'

Irritated, Harry repaired his plate with a wand flick and sent it soaring back into the air. After casting another Imperturbable Charm, he threw a book at it with all his might. It shattered noisily.

Harry felt Ron's eyes on his back as he bent over to pick up the pieces. 'Sorry,' he mumbled. 'We've just go so much work this year, and I can't bloody do this stupid fucking charm.'

'Here,' said Hermione. She crouched down over him and fixed the plate with her wand. When she had straightened up, she said, 'You're probably just tired, Harry.'

'I'm fine.'

But by the end of the lesson he still had made little progress with the charm.

The remainder of the day's classes went no better for Harry, as his headache worsened and made it impossible for him to concentrate. He tried and failed to rid himself of distractions outside of schoolwork, but though he had no difficulty ignoring Ron prattling on about Quidditch, it was far trickier to steer his thoughts from the visions, the dreams, and the possible meaning of MDIU.

He barely listened to Professor Aubrey speaking in his last class of the afternoon, Defence Against the Dark Arts. Though their new professor showed enthusiasm, he wasn't able to transfer this feeling to the students, many of whom were well versed in the spells he made them read about. He had designated their first lesson to theory rather than practice, and Harry's mind wandered as he stared at a chapter on the history of the Patronus – a spell that he had first mastered nearly five years ago.

Eventually the bell rang, and Harry gathered his things to head out of the Defence classroom with Ron and Hermione. The pair had agreed to visit Hagrid with him before dinner.

'So, just to make this absolutely clear –'

'No, Ron, he's not going to try out for Quidditch. And I don't think you should, either,' said Hermione seriously. 'Haven't you considered giving the other years a chance to play?'

'It's not like I'm stopping them! If they're good enough, they'll make the team.'

'But you've had much more practice! It's hardly fair.'

'Quidditch isn't about being fair, Hermione, it's about winning.'

'It's a waste of time.'

Hermione and Ron both paused in their arguing to turn to Harry for backup. He shrugged and carried on moving. After a moment's silence, their bickering started up again, providing a soundtrack to their walk through the castle and out onto the grounds.

It was a dry, cool afternoon, and the sun was still high in the sky, its rays bright and glaring. Harry squinted as he stepped across the grass and rubbed his eyes to try to displace the dull throbbing in his head. Rather than walk direct to Hagrid's cabin, he made a detour to the edge of the forest where the trees cast a welcoming shade. Hermione and Ron tramped behind him, their persistent squabbling ringing in Harry's ears.

Already Harry was regretting his decision to come down here. His body seemed to protest as he walked on, trying not to stumble, the sickness he felt earlier returning with full force. He knew he should have eaten something before leaving the castle; now he thought about it, it had been well over twenty-four hours since his last proper meal.

A loud cracking noise interrupted his thoughts, and Harry stopped short to turn and face the direction of the distraction. Someone was moving in the forest, lumbering over broken branches, lurching towards him...

Harry stood statue still as the figure neared him, the shape of its billowing black cloak becoming visible through the trees...

His thoughts lost all coherence as the memories assailed him: image after image of death, of snakes rearing and fangs sinking into flesh, of bones cracking and blood seeping and that terrible, awful screaming ... the crunch of breaking limbs against the backdrop of high, cold laughter ... the smell of fear and the feel of blood-drenched robes...

'Harry! Harry, wake up!'

His eyes shot open. Hermione and Ron were staring down at him, outlined by clear blue sky, fraught expressions on their faces. Harry felt something digging into his back and rolled sideways on the grass.

'We've got to get you to Pomfrey.'

'It's all right,' said Harry. He put his hands flat on the ground and pushed himself up to a kneeling position. He held his breath for a moment before breathing in deeply.

'Harry, you fainted,' said Hermione, crouching down. She placed her hand on his shoulder, rubbing his back in a soothing fashion.

'I didn't faint. I just ... tripped or something,' managed Harry. 'I'm fine.' He wondered how many times he had said that today.

'I don't know, mate...' Ron began, but Harry silenced him by grabbing his arm. He pulled himself to his feet, using Ron's grip as leverage.

'Let's just get to Hagrid's. We're much closer to him than Pomfrey, and I could do with sitting down.'

Harry saw his friends exchange a look, obviously trying to reach a silent decision.

'Hagrid's is closer,' said Hermione finally. 'Are you all right to walk, Harry?'

A few tentative steps indicated that he was not, and Ron and Hermione rushed to his side to stop him from falling. They walked to Hagrid's slowly, Harry's arms around his friends' shoulders as they propped him up.

After a few minutes, they reached the cabin, where Fang's barks boomed in reply to their knock on the door. There was a scuffling sound, and then Hagrid appeared before them, Fang at his side.

'Bou' time you three –' he started, before breaking off and taking in Harry's appearance. 'What's wrong with yeh? What's happened?' He moved to the left, pulling Fang with him, to let the three of them shuffle through the door.

'Harry fainted, Hagrid,' said Hermione over Harry's protestations. She and Ron manoeuvred him to the sofa where they all slumped down. 'Have you got any chocolate?'

Hagrid was still for a moment, staring at Harry in concern. Then he registered Hermione's request and flew into action. 'Chocolate, yeah, I think so. Hang on a minute.' And then he was rummaging around in the cupboards, Fang scrabbling at his feet. 'Lessee ... Know it's here somewhere ... aha!'

He returned a moment later with the largest chocolate bar Harry had ever seen, and sat down in the chair opposite to watch him eat it.

'Why'd yeh faint, Harry? An' don' go tellin' me yeh didn'.' Hagrid's beetle black eyes pierced into Harry's, who looked away.

'Missed lunch,' he muttered, swallowing a square of chocolate and breaking off another. 'But I feel much better now. How are you, Hagrid?'

'Why'd yeh miss lunch?'

'Forgot.'

Harry's cheeks burned as his friends once again exchanged looks. The urge to talk about anything else built with each second of their silence. 'Hagrid, what do you think of Petrova?' he said now. 'You were with her the other day in the Great Hall. Is she ... who is she? What's she like?'

The silence took on a different feel as Ron and Hermione straightened in their seats next to him, just as interested as he was to hear what Hagrid had to say.

'Yeh sure yeh're alrigh', Harry?'

He nodded frantically. 'Much better, really.' It wasn't a lie; Harry could already feel warmth from the chocolate sweeping through his body. 'I'll go to Pomfrey later anyway just in case. I swear.'

'Alrigh',' said Hagrid. 'So what do yeh want ter know about Petrova?'

The trio sat in rapt silence as Hagrid told them all he knew about their new professor, from his first impressions ('Brillian' woman, sharp like') to deeper feelings regarding her state of mind ('Used ter teach at Durmstrang, that'll have toughened her up a bit, but she's friendlier than she seems, lonely, I reckon').

'She was dead int'rested in Harry here. O' course, who isn't?'

'How d'you mean?' said Harry.

'She was askin' me abou' the final battle, abou' what yeh did an' everythin'. Told her all abou' it.'

'Oh,' said Harry. So that was what had made Petrova wary during the feast: Hagrid's description of him.

He turned to catch Hermione's eye; she smiled at him apologetically.

'Forgot me manners!' said Hagrid now. 'Didn' offer yeh tea or anythin'!' He stood up and lumbered over to the counter.

'We're fine, Hagrid,' said Ron quickly but to no avail: Hagrid was already returning with a tray of rock cakes.

An hour passed in which they drank tea, chatted, and ate, Hermione and Ron looking enviously at Harry's chocolate as they braved the rock cakes. Hagrid filled them in his latest acquisition of Graphorn eggs ('Grawpie likes ter play with them in the forest'), and Hermione and Ron talked for a while about Arithmancy and Quidditch. Eventually, when they were six rock cakes down and Ron was nursing his jaw, Harry suggested they ought to get back to start on their homework.

They said their goodbyes, promising to come back again soon, and headed up the grounds to the castle.

'Hospital Wing then?' said Hermione when they were back in the Entrance Hall. 'You did say you'd see Pomfrey.'

'But I'm fine now!' Harry protested.

Hermione frowned. 'All the same, people don't just faint for no reason...'

'Ron, tell her,' said Harry.

'Don't ask me,' said Ron, looking from his best friend to his girlfriend and shrugging. 'He seems all right now, but –'

'Exactly. Come on, Hermione, you can help me with that essay on Charms.'

Without waiting for an answer, Harry walked up the staircase to the first floor. He let out a sigh of relief when his friends followed behind him without further comments.

The evening was spent in a leisurely fashion as they huddled around a table in the Gryffindor common room and made an inroad into their workload, stopping only for dinner. Having put the finishing touches to his Charms essay, Harry played chess with Ron for a while and then headed to bed.

He was asleep the moment that his head touched the pillow, his dream taking him from the dormitory and depositing him in a new room that was unfamiliar yet similar to his own. Here, the same four-poster beds lined the circular wall of the tower, but no one stirred in them; he was alone and the room was quite bare.

Candlelight shone though a crack in a door to the left of him, and he gradually became aware of voices audible in the distance. Harry crept out of bed and slowly walked out of the dormitory, curiosity pulling him along.

The corridor was high and narrow, lit by flaming torches bracketed on the walls. A thin, red velvet runner lay across the floorboards, cushioning his feet. Harry padded along the corridor until it ended with a spiral staircase. From below him came the voices, clearer now. He could make out two separate people, one male, one female, and without hesitation, he started down the stairs towards them.

The bottom of the stairs opened into a large drawing room furnished with plush green armchairs at one end and a rosewood table at the other. Petrova and Snape were sitting next to each other at the table and did not look up as he walked past the armchairs towards them. Some part of Harry thought he ought to be surprised they were there, but he was not sure why; after all, it was obvious that the two professors belonged here.

Harry was standing in front of them now, but they continued to ignore him, their interest drawn to a book lying open on the table.

'What is it?' Harry asked, to no reply.

He leant over to examine the book. It was large and old, and the pages were filled with cramped lines of heavy black text interspersed with woodcuts.

'What is it?' he said again, more urgently now. There was something about the book – it felt terribly familiar, terribly important.

But they were rising from the table, not having heard him. Petrova walked past Harry towards the armchairs, while Snape gathered the book in his arms. Harry caught a brief glance of the spine before Snape's hands obscured it. The look was long enough for him to read the gold lettering of the title:

A TRAILE OF FOURE

Harry stepped back, gripped by sudden panic. Snape met his eyes.

'Find Malfoy,' he told Harry.