Harry did not mention his vague suspicions to Sirius, whose cheerfulness was evaporating fast now that Christmas was over. As the date of their departure back to Hogwarts drew nearer, he became more and more prone to what Mrs. Weasley called "fits of the sullens", in which he would become taciturn and grumpy, often withdrawing to Buckbeak's room for hours at a time. His gloom seeped through the house, oozing under doorways like some noxious gas, so that all of them became infected by it.

Kreacher, it transpired, had been lurking in the attic. Sirius said he had found him up there, covered in dust, no doubt looking for more relics of the Black family to hide in his cupboard. Though Sirius seemed satisfied with this story, it made Harry uneasy. Kreacher seemed to be in a better mood on his reappearance, his bitter muttering had subsided somewhat and he submitted to orders more docilely than usual, though once or twice Harry caught the house-elf staring at him avidly, but always looking quickly away whenever he saw that Harry had noticed.

Then, on the very last day of the holidays, something happened that made Harry positively dread his return to school.

Harry didn't want to leave Sirius again with only Kreacher for company; in fact, for the first time in his life, he was not looking forward to returning to Hogwarts. Going back to school would mean placing himself once again under the tyranny of Dolores Umbridge, who had no doubt managed to force through another dozen decrees in their absence; there was no Quidditch to look forward to now that he had been banned, there was every likelihood that their burden of homework would increase as the exams drew even nearer; and Dumbledore remained as remote as ever. In fact, if it hadn't been for the DA, Harry thought he might have begged Sirius to let him leave Hogwarts and remain in Grimmauld Place.

"Harry, dear," said Mrs. Weasley poking her head into his and Ron's bedroom, where the pair of them were playing wizard chess watched by Hermione, Ginny and Crookshanks, "could you come down to the kitchen? Professor Snape would like a word with you."

Harry did not immediately register what she had said; one of his castles was engaged in a violent tussle with a pawn of Ron's and he was egging it on enthusiastically.

"Professor Snape, dear. In the kitchen. He'd like a word."

"Squash him -- squash him, he's only a pawn, you idiot. Sorry, Mrs. Weasley, what did you say?"

"Snape?" said Harry blankly.

Harry's mouth fell open in horror. He looked around at Ron, Hermione and Ginny, all of whom were gaping back at him. Crookshanks, whom Hermione had been restraining with difficulty for the past quarter of an hour, leapt gleefully on to the board and set the pieces running for cover, squealing at the top of their voices.

"Professor Snape, dear," said Mrs. Weasley reprovingly. "Now come on, quickly, he says he can't stay long."

"What's he want with you?" said Ron, looking unnerved as Mrs. Weasley withdrew from the room. "You haven't done anything, have you?"

"No!" said Harry indignantly, racking his brains to think what he could have done that would make Snape pursue him to Grimmauld Place. Had his last piece of homework perhaps earned a 'T'?

Snape looked around at him, his face framed between curtains of greasy black hair.

A minute or two later, he pushed open the kitchen door to find Sirius and Snape both seated at the long kitchen table, glaring in opposite directions. The silence between them was heavy with mutual dislike. A letter lay open on the table in front of Sirius.

"Er," said Harry, to announce his presence.

"Sit down, Potter."

"You know," said Sirius loudly, leaning back on his rear chair legs and speaking to the ceiling, "I think I'd prefer it if you didn't give orders here, Snape. It's my house, you see."

An ugly flush suffused Snape's pallid face. Harry sat down in a chair beside Sirius, facing Snape across the table.

"I was supposed to see you alone, Potter," said Snape, the familiar sneer curling his mouth, "but Black --"

"I am here on Dumbledore's orders." said Snape, whose voice, by contrast, was becoming more and more quietly waspish, "but by all means stay, Black, I know you like to feel… involved."

"I'm his godfather," said Sirius, louder than ever.

"Study what?" said Harry blankly.

It was Sirius's turn to flush. Snape's lip curled in triumph as he turned to Harry.

"Merely that I am sure you must feel -- ah -- frustrated by the fact that you can do nothing useful," Snape laid a delicate stress on the word, "for the Order."

"The Headmaster has sent me to tell you, Potter, that it is his wish for you to study Occlumency this term."

Snape's sneer became more pronounced.

"Occlumency, Potter. The magical defence of the mind against external penetration. An obscure branch of magic, but a highly useful one."

"What's that supposed to mean?" said Sirius, letting his chair fall back on to all four legs with a loud bang.

Harry's heart began to pump very fast indeed. Defence against external penetration? But he was not being possessed, they had all agreed on that…

"Why do I have to study Occlu -- thing?" he blurted out.

"Because the Headmaster thinks it a good idea," said Snape smoothly. "You will receive private lessons once a week, but you will not tell anybody what you are doing, least of all Dolores Umbridge. You understand?"

Extra lessons with Snape -- what on earth had he done to deserve this? He looked quickly round at Sirius for support.

"I am in rather a hurry, Black. Unlike you, I do not have unlimited leisure time."

"I'll get to the point, then," said Sirius, standing up. He was rather taller than Snape who, Harry noticed, balled his fist in the pocket of his cloak over what Harry was sure was the handle of his wand. "If I hear you're using these Occlumency lessons to give Harry a hard time, you'll have me to answer to."

He turned to leave, his black travelling cloak billowing behind him.

"Why can't Dumbledore teach Harry?" asked Sirius aggressively. "Why you?"

Snape raised an eyebrow.

"Yes," said Harry. "Who's going to be teaching me?"

"I am," he said.

"Wait a moment," said Sirius, sitting up straighter in his chair.

Harry had the horrible sensation that his insides were melting.

"I suppose because it is a headmaster's privilege to delegate less enjoyable tasks," said Snape silkily. "I assure you I did not beg for the job." He got to his feet. "I will expect you at six o'clock on Monday evening, Potter. My office. If anybody asks, you are taking remedial Potions. Nobody who has seen you in my classes could deny you need them."

Snape turned back to face them, sneering.

"Yes, I have," said Sirius proudly.

"How touching," Snape sneered. "But surely you have noticed that Potter is very like his father?"

"Well then, you'll know he's so arrogant that criticism simply bounces off him," Snape said sleekly.

Sirius pushed his chair roughly aside and strode around the table towards Snape, pulling out his wand as he went. Snape whipped out his own. They were squaring up to each other, Sirius looking livid, Snape calculating, his eyes darting from Sirius's wand-tip to his face.

"Sirius!" said Harry loudly, but Sirius appeared not to hear him.

"Oh, but why don't you tell him so?" whispered Snape. "Or are you afraid he might not take very seriously the advice of a man who has been hiding inside his mother's house for six months?"

"Tell me, how is Lucius Malfoy these days? I expect he's delighted his lapdog's working at Hogwarts, isn't he?"

"I've warned you, Snivelus," said Sirius, his face barely a foot from Snape's, "I don't care if Dumbledore thinks you've reformed, I know better --"

"Are you calling me a coward?" roared Sirius, trying to push Harry out of the way, but Harry would not budge.

Sirius raised his wand.

"NO!" Harry yelled, vaulting over the table and trying to get in between them. "Sirius, don't!"

The kitchen door opened and the entire Weasley family, plus Hermione, came inside, all looking very happy, with Mr. Weasley walking proudly in their midst dressed in a pair of striped pyjamas covered by a mackintosh.

"Speaking of dogs," said Snape softly, "did you know that Lucius Malfoy recognised you last time you risked a little jaunt outside? Clever idea, Black, getting yourself seen on a safe station platform… gave you a cast-iron excuse not to leave your hidey-hole in future, didn't it?"

"Harry -- get -- out -- of -- it!" snarled Sirius, pushing him aside with his free hand.

"Why, yes, I suppose I am," said Snape.

"Cured!" he announced brightly to the kitchen at large. "Completely cured!"

He and all the other Weasleys froze on the threshold, gazing at the scene in front of them, which was also suspended in mid-action, both Sirius and Snape looking towards the door with their wands pointing into each other's faces and Harry immobile between them, a hand stretched out to each, trying to force them apart.

Both Sirius and Snape lowered their wands. Harry looked from one to the other. Each wore an expression of utmost contempt, yet the unexpected entrance of so many witnesses seemed to have brought them to their senses. Snape pocketed his wand, turned on his heel and swept back across the kitchen, passing the Weasleys without comment. At the door he looked back.

"Six o'clock, Monday evening, Potter."

"What's been going on?" asked Mr. Weasley again.

And he was gone. Sirius glared after him, his wand at his side.

"Nothing, Arthur," said Sirius, who was breathing heavily as though he had just run a long distance. "Just a friendly little chat between two old school friends." With what looked like an enormous effort, he smiled. "So… you're cured? That's great news, really great."

"Yes, isn't it?" said Mrs. Weasley, leading her husband forward to a chair. "Healer Smethwyck worked his magic in the end, found an antidote to whatever that snake's got in its fangs, and Arthur's learned his lesson about dabbling in Muggle medicine, haven't you, dear?" she added, rather menacingly.

"Merlin's beard," said Mr. Weasley, the smile sliding off his face, "what's going on here?"

"Dumbledore wants to stop you having those dreams about Voldemort," said Hermione at once. "Well, you won't be sorry not to have them any more, will you?"

"That night's meal should have been a cheerful one, with Mr. Weasley back amongst them. Harry could tell Sirius was trying to make it so, yet when his godfather was not forcing himself to laugh loudly at Fred and George's jokes or offering everyone more food, his face fell back into a moody, brooding expression. Harry was separated from him by Mundungus and Mad-Eye, who had dropped in to offer Mr. Weasley their congratulations. He wanted to talk to Sirius, to tell him he shouldn't listen to a word Snape said, that Snape was goading him deliberately and that the rest of them didn't think Sirius was a coward for doing as Dumbledore told him and remaining in Grimmauld Place. But he had no opportunity to do so, and, eyeing the ugly look on Sirius's face, Harry wondered occasionally whether he would have dared to mention it even if he had the chance. Instead, he told Ron and Hermione under his voice about having to take Occlumency lessons with Snape.

"Yes, Molly dear," said Mr. Weasley meekly.

They were to return to Hogwarts on the Knight Bus the following day, escorted once again by Tonks and Lupin, both of whom were eating breakfast in the kitchen when Harry, Ron and Hermione came down next morning. The adults seemed to have been mid-way through a whispered conversation as Harry opened the door; all of them looked round hastily and fell silent.

"Extra lessons with Snape?" said Ron, sounding aghast. "I'd rather have the nightmares!"

After a hurried breakfast, they all pulled on jackets and scarves against the chilly grey January morning. Harry had an unpleasant constricted sensation in his chest; he did not want to say goodbye to Sirius. He had a bad feeling about this parting; he didn't know when they would next see each other and he felt it was incumbent upon him to say something to Sirius to stop him doing anything stupid -- Harry was worried that Snape's accusation of cowardice had stung Sirius so badly he might even now be planning some foolhardy trip beyond Grimmauld Place. Before he could think of what to say, however, Sirius had beckoned him to his side.

"What is it?" Harry asked.

"I want you to take this," he said quietly, thrusting a badly wrapped package roughly the size of a paperback book into Harry's hands.

"Let's go, then," said Sirius, clapping Harry on the shoulder and smiling grimly, and before Harry could say anything else, they were heading upstairs, stopping before the heavily chained and bolted front door, surrounded by Weasleys.

"OK," said Harry, stowing the package away in the inside pocket of his jacket, but he knew he would never use whatever it was. It would not be he, Harry, who lured Sirius from his place of safety, no matter how foully Snape treated him in their forthcoming Occlumency classes.

"A way of letting me know if Snape's giving you a hard time. No, don't open it in here!" said Sirius, with a wary look at Mrs. Weasley, who was trying to persuade the twins to wear hand-knitted mittens. "I doubt Molly would approve -- but I want you to use it if you need me, all right?"

"Goodbye, Harry, take care," said Mrs. Weasley, hugging him.

"See you, Harry, and keep an eye out for snakes for me!" said Mr. Weasley genially, shaking his hand.

"Right -- yeah," said Harry distractedly; it was his last chance to tell Sirius to be careful; he turned, looked into his godfather's face and opened his mouth to speak, but before he could do so Sirius was giving him a brief, one-armed hug, and saying gruffly, "Look after yourself, Harry." Next moment, Harry found himself being shunted out into the icy winter air, with Tonks (today heavily disguised as a tall, tweedy woman with iron-grey hair) chivvying him down the steps.

The door of number twelve slammed shut behind them. They followed Lupin down the front steps. As he reached the pavement, Harry looked round. Number twelve was shrinking rapidly as those on either side of it stretched sideways, squeezing it out of sight. One blink later, it had gone.

"Come on, the quicker we get on the bus the better," said Tonks, and Harry thought there was nervousness in the glance she threw around the square. Lupin flung out his right arm.

A violently purple, triple-decker bus had appeared out of thin air in front of them, narrowly avoiding the nearest lamppost, which jumped backwards out of its way.

A thin, pimply, jug-eared youth in a purple uniform leapt down on to the pavement and said, "Welcome to the --"

"If you shout his name I will curse you into oblivion," muttered Tonks menacingly, now shunting Ginny and Hermione forwards.

"Yes, yes, we know, thank you," said Tonks swiftly. "On, on, get on --"

"I've always wanted to go on this thing," said Ron happily, joining Harry on board and looking around.

BANG.

"Ere -- it's "Arry --!"

And she shoved Harry forwards towards the steps, past the conductor, who goggled at Harry as he passed.

It had been evening the last time Harry had travelled by Knight Bus and its three decks had been full of brass bedsteads. Now, in the early morning, it was crammed with an assortment of mismatched chairs grouped haphazardly around windows. Some of these appeared to have fallen over when the bus stopped abruptly in Grimmauld Place; a few witches and wizards were still getting to their feet, grumbling, and somebody's shopping bag had slid the length of the bus: an unpleasant mixture of frogspawn, cockroaches and custard creams was scattered all over the floor.

"Looks like we'll have to split up," said Tonks briskly, looking a. round for empty chairs. "Fred, George and Ginny, if you just take those seats at the back… Remus can stay with you."

She, Harry, Ron and Hermione proceeded up to the very top deck, where there were two unoccupied chairs at the very front of the bus and two at the back. Stan Shunpike, the conductor, followed Harry and Ron eagerly to the back. Heads turned as Harry passed and, when he sat down, he saw all the faces flick back to the front again.

As Harry and Ron handed Stan eleven Sickles each, the bus set off again, swaying ominously. It rumbled around Grimmauld Place, weaving on and off the pavement, then, with another tremendous BANG, they were all flung backwards; Ron's chair toppled right over and Pigwidgeon, who had been on his lap, burst out of his cage and flew twittering wildly up to the front of the bus where he fluttered down on to Hermione's shoulder instead. Harry, who had narrowly avoided falling by seizing a candle bracket, looked out of the window: they were now speeding down what appeared to be a motorway.

"Just outside Birmingham," said Stan happily, answering Harry's unasked question as Ron struggled up from the floor. "You keeping well, then, "Arry? I seen your name in the paper loads over the summer, but it weren't never nuffink very nice. I said to Ern, I said, "e didn't seem like a nutter when we met "im, just goes to show, dunnit?"

Chairs slid backwards again as the Knight Bus jumped from the Birmingham motorway to a quiet country lane full of hairpin bends. Hedgerows on either side of the road were leaping out of their way as they mounted the verges. From here they moved to a main street in the middle of a busy town, then to a viaduct surrounded by tall hills, then to a windswept road between high-rise flats, each time with a loud BANG.

He handed over their tickets and continued to gaze, enthralled, at Harry. Apparently, Stan did not care how nutty somebody was, if they were famous enough to be in the paper. The Knight Bus swayed alarmingly, overtaking a line of cars on the inside. Looking towards the front of the bus, Harry saw Hermione cover her eyes with her hands, Pigwidgeon swaying happily on her shoulder.

BANG.

"I've changed my mind," muttered Ron, picking himself up from the floor for the sixth time, "I never want to ride on this thing again."

"Listen, it's "Ogwarts stop after this," said Stan brightly, swaying towards them. "That bossy woman up front "oo got on with you, she's given us a little tip to move you up the queue. We're just gonna let Madam Marsh off first, though -- there was a retching sound from downstairs, followed by a horrible spattering noise -- she's not feeling "er best."

BANG.

A few minutes later, the Knight Bus screeched to a halt outside a small pub, which squeezed itself out of the way to avoid a collision. They could hear Stan ushering the unfortunate Madam Marsh out of the bus and the relieved murmurings of her fellow passengers on the second deck. The bus moved on again, gathering speed, until --

They were rolling through a snowy Hogsmeade. Harry caught a glimpse of the Hog's Head down its side street, the severed boar's head sign creaking in the wintry wind. Flecks of snow hit the large window at the front of the bus. At last they rolled to a halt outside the gates to Hogwarts.

Lupin and Tonks helped them off the bus with their luggage, then got off to say goodbye. Harry glanced up at the three decks of the Knight Bus and saw all the passengers staring down at them, noses flat against the windows.

"Yeah, all right," said Harry heavily, looking up into Lupin's prematurely lined face. "See you, then."

The six of them struggled up the slippery drive towards the castle, dragging their trunks. Hermione was already talking about knitting a few elf hats before bedtime. Harry glanced back when they reached the oaken front doors; the Knight Bus had already gone and he half-wished, given what was coming the following evening, that he was still on board.

"You'll be safe once you're in the grounds," said Tonks, casting a careful eye around at the deserted road. "Have a good term, OK?"

"Look after yourselves," said Lupin, shaking hands all round and reaching Harry last. "And listen…" he lowered his voice while the rest of them exchanged last-minute goodbyes with Tonks, "Harry, I know you don't like Snape, but he is a superb Occlumens and we all -- Sirius included -- want you to learn to protect yourself, so work hard, all right?"

"I'll let you know in the usual way when the next one is," Harry said over and over again, "but I can't do it tonight, I've got to go to -- er -- remedial Potions."

"You take remedial Potions?" asked Zacharias Smith superciliously, having cornered Harry in the Entrance Hall after lunch. "Good Lord, you must be terrible. Snape doesn't usually give extra lessons, does he?"

Harry spent most of the next day dreading the evening. His morning double-Potions lesson did nothing to dispel his trepidation, as Snape was as unpleasant as ever. His mood was further lowered by the DA members constantly approaching him in the corridors between classes, asking hopefully if there would be a meeting that night.

"Shall I jinx him? I can still get him from here," he said, raising his wand and taking aim between Smith's shoulder blades.

As Smith strode away in an annoyingly buoyant fashion, Ron glared after him.

"Forget it," said Harry dismally. "It's what everyone's going to think, isn't it? That I'm really stup --"

"Hi, Harry," said a voice behind him. He turned round and found Cho standing there.

She walked away. Harry stood staring after her, his brain working frantically. Then something clunked into place.

"I -- er --" he said.

"Oh, it's OK if you don't," she said, looking mortified. "Don't worry. I -- I'll see you around."

"Yeah, not bad," said Harry.

"Right," said Harry, wondering why she was telling him this. "Well, I suppose you want to --?"

"What? Oh, no, I haven't checked the noticeboard since I got back."

"Only if you do," she said eagerly.

"Yes, it's on Valentines Day…"

"We'll be in the library, Harry," said Hermione firmly as she seized Ron above the elbow and dragged him off towards the marble staircase.

"Oh," said Harry as his stomach leapt uncomfortably. "Hi."

"Mine was pretty quiet," said Cho. For some reason, she was looking rather embarrassed. "Erm… there's another Hogsmeade trip next month, did you see the notice?"

Harry stared. He had been about to say, "I suppose you want to know when the next DA meeting is?" but her response did not seem to fit.

"Had a good Christmas?" asked Cho.

He ran after her, catching her halfway up the marble staircase.

"Cho! Hey -- CHO!"

"Er -- d'you want to come into Hogsmeade with me on Valentine's Day?"

By six o'clock that evening, however, even the glow of having successfully asked out Cho Chang could not lighten the ominous feelings that intensified with every step Harry took towards Snape's office.

"Oooh, yes!" she said, blushing crimson and beaming at him.

"Right… well… that's settled then," said Harry, and feeling that the day was not going to be a complete loss after all, he virtually bounced off to the library to pick up Ron and Hermione before their afternoon lessons.

The shadowy room was lined with shelves bearing hundreds of glass jars in which slimy bits of animals and plants were suspended in variously coloured potions. In one corner stood the cupboard full of ingredients that Snape had once accused Harry -- not without reason -- of robbing. Harry's attention was drawn towards the desk, however, where a shallow stone basin engraved with runes and symbols lay in a pool of candlelight. Harry recognised it at once -- it was Dumbledore's Pensieve. Wondering what on earth it was doing there, he jumped when Snape's cold voice came out of the shadows.

He paused outside the door when he reached it, wishing he were almost anywhere else, then, taking a deep breath, he knocked and entered.

"Right," said Harry tersely.

Harry did as he was told, with the horrible feeling that he was imprisoning himself. When he turned back into the room, Snape had moved into the light and was pointing silently at the chair opposite his desk. Harry sat down and so did Snape, his cold black eyes fixed unblinkingly upon Harry, dislike etched in every line of his face.

"Well, Potter, you know why you are here," he said. "The Headmaster has asked me to teach you Occlumency. I can only hope that you prove more adept at it than at Potions."

"Shut the door behind you, Potter."

"This may not be an ordinary class, Potter," said Snape, his eyes narrowed malevolently, "but I am still your teacher and you will therefore call me 'sir' or 'Professor' at all times."

"And why does Professor Dumbledore think I need it, sir?" said Harry looking directly into Snape's eyes and wondering whether Snape would answer.

Snape continued to survey him through narrowed eyes for a moment, then said, "Now, Occlumency. As I told you back in your dear godfather's kitchen, this branch of magic seals the mind against magical intrusion and influence."

"Yes… sir," said Harry.

"It is the ability to extract feelings and memories from another person's mind --"

"What's that? Sir?"

Snape looked back at him for a moment and then said contemptuously, "Surely even you could have worked that out by now, Potter? The Dark Lord is highly skilled at Legilimency --"

"He can read minds?" said Harry quickly, his worst fears confirmed.

Snape paused for a moment, apparently to savour the pleasure of insulting Harry, before continuing. "Only Muggles talk of 'mind-reading'. The mind is not a book, to be opened at will and examined at leisure. Thoughts are not etched on the inside of skulls, to be perused by any invader, the mind is a complex and many-layered thing, Potter -- or at least, most minds are." He smirked. "It is true, however, that those who have mastered Legilimency are able, under certain conditions, to delve into the minds of their victims and to interpret their findings correctly. The Dark Lord, for instance, almost always knows when somebody is lying to him. Only those skilled at Occlumency are able to shut down those feelings and memories that contradict the lie, and so can utter falsehoods in his presence without detection."

"You have no subtlety, Potter," said Snape, his dark eyes glittering. "You do not understand fine distinctions. It is one of the shortcomings that makes you such a lamentable potion-maker."

"So he could know what we're thinking right now? Sir?"

Whatever Snape said, Legilimency sounded like mind-reading to Harry, and he didn't like the sound of it at all.

"Well then, why do I have to learn Occlumency?"

"The usual rules do not seem to apply with you, Potter. The curse that failed to kill you seems to have forged some kind of connection between you and the Dark Lord. The evidence suggests that at times, when your mind is most relaxed and vulnerable -- when you are asleep, for instance -- you are sharing the Dark Lord's thoughts and emotions. The Headmaster thinks it inadvisable for this to continue. He wishes me to teach you how to close your mind to the Dark Lord."

Snape eyed Harry, tracing his mouth with one long, thin finger as he did so.

"The Dark Lord is at a considerable distance and the walls and grounds of Hogwarts are guarded by many ancient spells and charms to ensure the bodily and mental safety of those who dwell within them," said Snape. "Time and space matter in magic, Potter. Eye contact is often essential to Legilimency."

"But why does Professor Dumbledore want to stop it?" he asked abruptly. "I don't like it much, but it's been useful, hasn't it? I mean… I saw that snake attack Mr Weasley and if I hadn't, Professor Dumbledore wouldn't have been able to save him, would he? Sir?"

Harry's heart was pumping fast again. None of this added up.

"The one with the snake and Mr. Weasley?"

Snape stared at Harry for a few moments, still tracing his mouth with his finger. When he spoke again, it was slowly and deliberately, as though he weighed every word.

"It appears that the Dark Lord has been unaware of the connection between you and himself until very recently. Up till now it seems that you have been experiencing his emotions, and sharing his thoughts, without his being any the wiser. However, the vision you had shortly before Christmas --"

"Do not interrupt me, Potter," said Snape in a dangerous voice. "As I was saying, the vision you had shortly before Christmas represented such a powerful incursion upon the Dark Lord's thoughts --"

"I saw inside the snake's head, not his!"

But Harry did not care if Snape was angry; at last he seemed to be getting to the bottom of this business; he had moved forwards in his chair so that, without realising it, he was perched on the very edge, tense as though poised for flight.

"How come I saw through the snake's eyes if it's Voldemort's thoughts I'm sharing?"

"Do not say the Dark Lord's name!" spat Snape.

"I thought I just told you not to interrupt me, Potter?"

"I just wanted to know," Harry began again, forcing his voice back to politeness, "why --"

There was a nasty silence. They glared at each other across the Pensieve.

"You seem to have visited the snake's mind because that was where the Dark Lord was at that particular moment," snarled Snape. "He was possessing the snake at the time and so you dreamed you were inside it, too."

"Professor Dumbledore says his name." said Harry quietly.

"Dumbledore is an extremely powerful wizard," Snape muttered. "While he may feel secure enough to use the name… the rest of us…" He rubbed his left forearm, apparently unconsciously, on the spot where Harry knew the Dark Mark was burned into his skin.

"It is enough that we know," said Snape repressively. "The important point is that the Dark Lord is now aware that you are gaining access to his thoughts and feelings. He has also deduced that the process is likely to work in reverse; that is to say, he has realised that he might be able to access your thoughts and feelings in return --"

"And Vol -- he -- realised I was there?"

"It seems so," said Snape coolly.

"How do you know?" said Harry urgently. "Is this just Professor Dumbledore guessing, or --?"

"I told you," said Snape, rigid in his chair, his eyes slits, "to call me "sir".

Snape pulled out his wand from an inside pocket of his robes and Harry tensed in his chair, but Snape merely raised the wand to his temple and placed its tip into the greasy roots of his hair. When he withdrew it, some silvery substance came away, stretching from temple to wand like a thick gossamer strand, which broke as he pulled the wand away from it and fell gracefully into the Pensieve, where it swirled silvery-white, neither gas nor liquid. Twice more, Snape raised the wand to his temple and deposited the silvery substance into the stone basin, then, without offering any explanation of his behaviour, he picked up the Pensieve carefully, removed it to a shelf out of their way and returned to face Harry with his wand held at the ready.

"And he might try and make me do things?" asked Harry. "Sir?" he added hurriedly.

"He might," said Snape, sounding cold and unconcerned. "Which brings us back to Occlumency."

"Yes, sir," said Harry impatiently, "but how do you know --'?

Harry got to his feet, feeling nervous. They faced each other with the desk between them.

"Stand up and take out your wand, Potter."

Snape had struck before Harry was ready, before he had even begun to summon any force of resistance. The office swam in front of his eyes and vanished; image after image was racing through his mind like a flickering film so vivid it blinded him to his surroundings.

"And what are you going to do?" Harry asked, eyeing Snape's wand apprehensively.

"I am about to attempt to break into your mind," said Snape softly. "We are going to see how well you resist. I have been told that you have already shown aptitude at resisting the Imperius Curse. You will find that similar powers are needed for this… brace yourself, now. Legilimens!"

"You may use your wand to attempt to disarm me, or defend yourself in any other way you can think of," said Snape.

He was five, watching Dudley riding a new red bicycle, and his heart was bursting with jealousy… he was nine, and Ripper the bulldog was chasing him up a tree and the Dursleys were laughing below on the lawn… he was sitting under the Sorting Hat, and it was telling him he would do well in Slytherin… Hermione was lying in the hospital wing, her face covered with thick black hair… a hundred dementors were closing in on him beside the dark lake… Cho Chang was drawing nearer to him under the mistletoe…

"Did you mean to produce a Stinging Hex?" asked Snape coolly.

"I thought not," said Snape, watching him closely. "You let me get in too far. You lost control."

He felt a sharp pain in his knee. Snape's office had come back into view and he realised that he had fallen to the floor; one of his knees had collided painfully with the leg of Snape's desk. He looked up at Snape, who had lowered his wand and was rubbing his wrist. There was an angry weal there, like a scorch mark.

"No," said Harry bitterly, getting up from the floor.

No, said a voice inside Harry's head, as the memory of Cho drew nearer, you're not watching that, you're not watching it, it's private --

"Flashes of it," said Snape, his lip curling. "To whom did the dog belong?"

"Did you see everything I saw?" Harry asked, unsure whether he wanted to hear the answer.

"My Aunt Marge," Harry muttered, hating Snape.

"Well, for a first attempt that was not as poor as it might have been," said Snape, raising his wand once more. "You managed to stop me eventually, though you wasted time and energy shouting. You must remain focused. Repel me with your brain and you will not need to resort to your wand."

Harry was on his knees again, his face buried in his hands, his brain aching as though someone had been trying to pull it from his skull.

"Clear your mind, Potter," said Snape's cold voice. "Let go of all emotion…"

Harry threw him a filthy look before doing as he was told. He did not like the idea of standing there with his eyes shut while Snape faced him, carrying a wand.

"I'm trying," said Harry angrily, "but you're not telling me how!"

Harry tried to empty his mind, tried not to think, or remember, or feel…

But Harry's anger at Snape continued to pound through his veins like venom. Let go of his anger? He could as easily detach his legs…

A great black dragon was rearing in front of him… his father and mother were waving at him out of an enchanted mirror… Cedric Diggory was lying on the ground with blank eyes staring at him…

"Manners, Potter," said Snape dangerously. "Now, I want you to close your eyes."

"You're not doing it, Potter… you will need more discipline than this… focus, now…"

"Let's go again… on the count of three… one -- two -- three -- Legilimens!"

"NOOOOOOO!"

"I -- am -- making -- an -- effort," he said through clenched teeth.

Snape looked paler than usual, and angrier, though not nearly as angry as Harry was.

"Then you will find yourself easy prey for the Dark Lord!" said Snape savagely. "Fools who wear their hearts proudly on their sleeves, who cannot control their emotions, who wallow in sad memories and allow themselves to be provoked so easily -- weak people, in other words -- they stand no chance against his powers! He will penetrate your mind with absurd ease, Potter!"

"I am not weak," said Harry in a low voice, fury now pumping through him so that he thought he might attack Snape in a moment.

"Yeah? Well, I'm finding that hard at the moment," Harry snarled.

"Get up!" said Snape sharply. "Get up! You are not trying, you are making no effort. You are allowing me access to memories you fear, handing me weapons!"

Harry stood up again, his heart thumping wildly as though he had really just seen Cedric dead in the graveyard.

"I told you to empty yourself of emotion!"

"Realised what?" asked Snape sharply.

"Then prove it! Master yourself!" spat Snape. "Control your anger, discipline your mind! We shall try again! Get ready, now! Legilimens!"

He was watching Uncle Vernon hammering the letterbox shut… a hundred dementors were drifting across the lake in the grounds towards him… he was running along a windowless passage with Mr. Weasley… they were drawing nearer to the plain black door at the end of the corridor… Harry expected to go through it… but Mr. Weasley led him off to the left, down a flight of stone steps…

"I KNOW! I KNOW!"

"I saw -- I remembered," Harry panted. "I've just realised…"

"What happened then, Potter?" he asked, eyeing Harry intently.

He was on all fours again on Snape's office floor, his scar was prickling unpleasantly, but the voice that had just issued from his mouth was triumphant. He pushed himself up again to find Snape storing at him, his wand raised. It looked as though, this time, Snape had lifted the spell before Harry had even tried to fight back.

He had been dreaming about a windowless corridor ending in a locked door for months, without once realising that it was a real place. Now, seeing the memory again, he knew that all along he had been dreaming about the corridor down which he had run with Mr. Weasley on the twelfth of August as they hurried to the courtrooms in the Ministry; it was the corridor leading to the Department of Mysteries and Mr. Weasley had been there the night that he had been attacked by Voldemort's snake.

"What's in the Department of Mysteries?"

Harry did not answer at once; he was still savouring the moment of blinding realisation as he rubbed his forehead…

"Because," said Harry, watching Snape's face closely, "that corridor I've just seen -- I've been dreaming about it for months -- I've just recognised it -- it leads to the Department of Mysteries… and I think Voldemort wants something from --"

"I said, what's in the Department of Mysteries, sir?" Harry said.

"What did you say?" Snape asked quietly and Harry saw, with deep satisfaction, that Snape was unnerved.

He looked up at Snape.

"And why," said Snape slowly, "would you ask such a thing?"

They glared at each other. Harry's scar seared again, but he did not care. Snape looked agitated; but when he spoke again he sounded as though he was trying to appear cool and unconcerned.

"I have told you not to say the Dark Lord's name!"

"Yes," Harry said, still rubbing his prickling scar, which was becoming more painful.

"I want you back here same time on Wednesday. We will continue work then."

"You are to rid your mind of all emotion every night before sleep; empty it, make it blank and calm, you understand?"

"There are many things in the Department of Mysteries, Potter, few of which you would understand and none of which concern you. Do I make myself plain?"

"And be warned, Potter… I shall know if you have not practised…"

"Fine," said Harry. He was desperate to get out of Snape's office and find Ron and Hermione.

"Yes," said Harry, who was barely listening.

"Right," Harry mumbled. He picked up his schoolbag, swung it over his shoulder and hurried towards the office door. As he opened it, he glanced back at Snape, who had his back to Harry and was scooping his own thoughts out of the Pensieve with the tip of his wand and replacing them carefully inside his own head. Harry left without another word, closing the door carefully behind him, his scar still throbbing painfully.

Harry felt shivery; his scar was still aching, he felt almost feverish.

Harry found Ron and Hermione in the library, where they were working on Umbridge's most recent ream of homework. Other students, nearly all of them fifth-years, sat at lamp-lit tables nearby, noses close to books, quills scratching feverishly, while the sky outside the mullioned windows grew steadily blacker. The only other sound was the slight squeaking of one of Madam Pince's shoes, as the librarian prowled the aisles menacingly, breathing down the necks of those touching her precious books.

When he sat down opposite Ron and Hermione, he caught sight of himself in the window opposite; he was very white and his scar seemed to be showing up more clearly than usual.

"Yeah… fine… I dunno," said Harry impatiently, wincing as pain shot through his scar again. "Listen… I've just realised something…"

"How did it go?" Hermione whispered, and then, looking concerned. "Are you all right, Harry?"

And he told them what he had just seen and deduced.

Hermione let out a long, slow sigh. "Of course," she breathed.

"In the Department of Mysteries, it's got to be," Harry whispered. "I saw that door when your dad took me down to the courtrooms for my hearing and it's definitely the same one he was guarding when the snake bit him."

"How come Sturgis was trying to break in when he's on our side?" said Ron.

"So… so are you saying…" whispered Ron, as Madam Pince swept past, squeaking slightly "that the weapon -- the thing You-Know-Who's after -- is in the Ministry of Magic?"

"Of course what?" said Ron rather impatiently.

"Ron, think about it… Sturgis Podmore was trying to get through a door at the Ministry of Magic… it must have been that one, it's too much of a coincidence!"

"Well, I don't know," Hermione admitted. "That is a bit odd…"

"So what's in the Department of Mysteries?" Harry asked Ron. "Has your dad ever mentioned anything about it?"

"I know they call the people who work in there 'Unspeakables'," said Ron, frowning. "Because no one really seems to know what they do -- weird place to have a weapon."

"I expect anyone would feel snaky if they'd had their mind attacked over and over again," said Hermione sympathetically. "Look, let's get back to the common room, we'll be a bit more comfortable there."

"Headless Hats!" shouted George, as Fred waved a pointed hat decorated with a fluffy pink feather at the watching students. "Two Galleons each, watch Fred, now!"

For Harry had just run both his hands hard over his forehead as though trying to iron it.

"It's not weird at all, it makes perfect sense," said Hermione. "It will be something top secret that the Ministry has been developing, I expect… Harry, are you sure you're all right?"

"Yeah… fine…" he said, lowering his hands, which were trembling. "I just feel a bit… I don't like Occlumency much."

Fred swept the hat on to his head, beaming. For a second he merely looked rather stupid; then both hat and head vanished.

But the common room was packed and full of shrieks of laughter and excitement; Fred and George were demonstrating their latest bit of joke shop merchandise.

"How do those hats work, then?" said Hermione, distracted from her homework and watching Fred and George closely. "I mean, obviously it's some kind of Invisibility Spell, but it's rather clever to have extended the field of invisibility beyond the boundaries of the charmed object… I'd imagine the charm wouldn't have a very long life though."

"And off again!" shouted George, and Fred's hand groped for a moment in what seemed to be thin air over his shoulder; then his head reappeared as he swept the pink-feathered hat from it.

Several girls screamed, but everyone else was roaring with laughter.

"I'm going to have to do this tomorrow," he muttered, pushing the books he had just taken out of his bag back inside it.

Harry did not answer; he was feeling ill.

Harry and Ron exchanged looks as he reached into his bag, withdrew the planner and opened it tentatively.

"Don't leave it till later, you big second-rater!" chided the book as Harry scribbled down Umbridge's homework. Hermione beamed at it.

"Well, write it in your homework planner then!" said Hermione encouragingly. "So you don't forget!"

Maniacal laughter was ringing in his ears… he was happier than he had been in a very long time… jubilant, ecstatic, triumphant… a wonderful, wonderful thing had happened…

He walked across the common room, dodging George, who tried to put a Headless Hat on him, and reached the peace and cool of the stone staircase to the boys' dormitories. He was feeling sick again, just as he had the night he had had the vision of the snake, but thought that if he could just lie down for a while he would be all right.

He opened the door of his dormitory and was one step inside it when he experienced pain so severe he thought that someone must have sliced into the top of his head. He did not know where be was, whether he was standing or lying down, he did not even know his own name.

"I think I'll go to bed," said Harry, stuffing the homework planner back into his bag and making a mental note to drop it in the fire the first opportunity he got.

"Harry? HARRY!"

Someone had hit him around the face. The insane laughter was punctuated with a cry of pain. The happiness was draining out of him, but the laughter continued…

He opened his eyes and, as he did so, he became aware that the wild laughter was coming out of his own mouth. The moment he realised this, it died away; Harry lay panting on the floor, staring up at the ceiling, the scar on his forehead throbbing horribly. Ron was bending over him, looking very worried.

"I… dunno…" Harry gasped, sitting up again. "He's really happy… really happy…"

"What happened?" he said.

The words came, just as they had back in the Gryffindor changing room, as though a stranger was speaking them through Harry's mouth, yet he knew they were true. He took deep breaths, willing himself not to vomit all over Ron. He was very glad that Dean and Seamus were not here to watch this time.

"Hermione told me to come and check on you," said Ron in a low voice, helping Harry to his feet. "She says your defences will be low at the moment, after Snape's been fiddling around with your mind… still, I suppose it'll help in the long run, won't it?" strengthening it, and he wondered, with a feeling of great trepidation, what had happened to make Lord Voldemort the happiest he had been in fourteen years.

"Something good's happened," mumbled Harry. He was shaking as badly as he had done after seeing the snake attack Mr. Weasley and felt very sick. "Something he's been hoping for."

"You-Know-Who is?"

He looked doubtfully at Harry as he helped him towards his bed. Harry nodded without any conviction and slumped back on his pillows, aching all over from having fallen to the floor so often that evening, his scar still prickling painfully. He could not help feeling that his first foray into Occlumency had weakened his mind's resistance rather than