Disclaimer: By Anglo-American law, J.K. Rowling owns the Harry Potter concepts. Philosophically speaking, I'm not sure whether it's possible to own a concept. Either way, I know I don't own them.

Author's note: I know that Christmas stories are unusual in the middle of Holy Week, and that stories about the disastrous consequences of British/American linguistic-usage differences are unusual any time of year. What can I say? You write what the Muse tells you to write, especially when your Muse is as pushy as mine is.

"I heard that, Solomon."

Quiet, Erineae. Anyway, on with the story.

It was, in retrospect, the most evitable crisis in Hogwarts history. It could have been avoided, for instance, if Professor Burbage had been handling the request list; she knew something about Muggle sporting equipment, and she didn't think of everything in terms of figures. Or if Cricketshorn University had been located somewhere other than America; then Professor Vector wouldn't have felt the need to translate the term, and the confusion would have been choked off at the source. Or even if Professor Binns hadn't been such a cockeyed optimist.

However, none of these precautions – in hindsight so obvious – were taken, with the result that, on 25 December 1990, Hogwarts School of Witchcraft and Wizardry was nearly destroyed by 4,000,000,000,000,000 expressions of American goodwill.

It started when Rubeus Hagrid appeared in Professor McGonagall's office at about half-past seven on the 18th, his teeth chattering, his hair and beard dripping, and his lips an almost regal shade of blue.

He lumbered over to her desk and dropped a basket containing fourteen black, sopping-wet billiard balls. "'Ere yeh are, Professor," he shivered. "M-m-managed ter save th-that many, anyway. Dunno where the l-l-last four got ter."

"Thank you, Hagrid," Professor McGonagall sighed. "That was most commendable of you."

"J-j-just doin' me job, P-P-Professor," said Hagrid.

"Yes," said McGonagall. "And now I think you'd best get up to the hospital wing and let Madam Pomfrey do hers. We hardly need our gamekeeper coming down with pneumonia just before Christmas."

Hagrid nodded vaguely and left the room, leaving McGonagall to pick up the basket of billiard balls and place it beneath her desk, all the while murmuring dark imprecations against Peeves the Poltergeist. She had just exhausted her vocabulary of English imprecations, and was beginning to draw on her native Gaelic, when a gentle cough alerted her that she was not alone.

"Minerva?" came the hesitant voice of Theano Vector. "Do you have a minute?"

Professor McGonagall glanced up at the young Arithmancy teacher. "Oh, yes, certainly, Theano," she said, straightening and brushing dust off her robes. "I'm sorry, I've been having a bit of trouble with our resident knock-bogle."

Professor Vector's sympathetic glance indicated that such trouble was not restricted to the Transfiguration department. "Of course, yes," she said. "I don't mean to bother you, but I was just wondering if you wanted to put anything down for the Christmas Exchange."

McGonagall frowned. "The Christmas Exchange?"

"Yes," said Theano. "You know, the annual tradition in which the Hogwarts and Cricketshorn faculties send gifts to each other?"

"Oh, yes," said McGonagall. "Are we doing that today?"

"Well, no, we're doing it on Christmas, of course," said Theano, "but the Headmaster wanted me to send our list off today so that the folks on the other end had plenty of time to find everything by the 25th. I suppose Headmistress Spithaler's doing the same thing on her side of the pond."

She spoke in her usual abstracted, matter-of-fact tones, but there was a distinct undercurrent of pride in her voice. Theano Vector was the most junior member of the Hogwarts faculty (always excepting Defense against the Dark Arts), and to have Albus Dumbledore entrust her with any task of importance seemed to her a precious sign of confidence in her, even if it was only a minor clerical duty that Dumbledore generally assigned alphabetically by professors' surnames. (Sybill Trelawney had handled the Christmas Exchange the previous year, which had resulted in a good deal of confusion about what items her nebulous descriptions were supposed to signify; Professor Snape, for instance, had gotten a tennis racquet when he had asked for a seaweed strainer.)

"Anyway," she said, "Ramanujan's waiting for me in the Owlery, so very quickly: did you want the Americans to send you anything for Christmas?"

McGonagall was about to shake her head and say no, she was subsisting quite comfortably, when she remembered the items Peeves had deprived her of. "Yes," she said. "Four billiard balls."

Theano blinked. "Four billiard balls?" she repeated.

"Yes," said McGonagall. "The black kind, with the little 8's on them. I'm going to have the sixth years transfigure them into lumps of coal at the beginning of next term."

"Oh," Theano murmured. She seemed a trifle dazed, but McGonagall thought nothing of that; that was the Arithmancy teacher's habitual expression outside her classroom, and, indeed (in McGonagall's experience), the habitual expression of all arithmancers when they weren't occupied in reducing everything in the physical universe to one of nine digits.

"Well," she said vaguely, "I'll put that on the list, then."

"That would be very kind," said McGonagall. "Thank you."

After another few moments' hesitation, Theano left the room, and Professor McGonagall pulled a sheaf of students' term papers toward her and forgot about the whole affair for two weeks – at the end of which time, she would be astonished that she could ever have been so laissez-faire.

Theano Vector's mind, as she made her way to the Owlery, was awhirl. She had heard several unusual requests from various faculty members, but none of them had been as outlandish as Minerva's – and none had been delivered with such offhand casualness.

Four billiard balls? Four billiard balls? Just how many spares did Minerva plan to need?

Of course, she had never taken N.E.W.T.-level Transfiguration, so she had no real idea what went on in those classes. Maybe there was a class in which Minerva's passel of overachievers were required to transfigure large numbers of similar objects at once; maybe this was a necessary skill in some arcane area of expertise.

But still – four billiard?

Theano sighed. Oh, well, she would put it in the letter, and let them puzzle it out on the other end. Presumably Spithaler had taken Advanced Transfiguration; maybe the request would convey something to her.

About fifteen minutes later, Theano was returning to her office, feeling remarkably pleased with herself. She had managed to navigate the entire Owlery without upsetting more than two perches; she had written the letter in a legible hand, rather than the vaguely sinusoidal scrawl she usually used; and she had even remembered the American word for "billiard".

Alexandra Spithaler, Headmistress of Cricketshorn University of Enchantment and the Liberal Arts, was gazing dreamily into the large lodestone on her desk when she heard a peculiar tapping sound on her eastern office window. She glanced up, and saw an astonishingly bedraggled tawny owl perched on the windowsill, a rolled-up sheet of parchment tied to its leg.

Spithaler frowned. Tawny owls were a distinctively Old-World species; what was one doing in the middle of the Rocky Mountains?

"Oh, of course," she muttered, smacking her forehead. "The Christmas Exchange." Hastily, she went over to the window, scurried up the stepladder, and drew the mournfully hooting bird onto her arm.

"There, there, boy," she cooed. "Have those nasty Englishmen been sending you across the Atlantic again?" (Spithaler herself considered using owls – even magical ones – for transoceanic communication to be cruel and barbaric as well as grossly inefficient; Cricketshorn's Christmas Exchange list had been sent as an enchanted paper airplane.)

She detached the paper from Ramanujan's leg, then summoned her secretary, Mary McCadden, to take him to Professor Ziarnik of Magical Zoology for "a bit of nice rest and pampering". This done, she unrolled the parchment and sat down at her desk to peruse it.

Most of the list was eminently sensible and traditional: socks for Dumbledore, candies for Flitwick, good-luck charms for that year's Defense against the Dark Arts professor, that sort of thing. It was only the last item that caused Spithaler to rub her eyes, reread it four or five times, and wonder whether the spell that had kept her body frozen at the age of six for the past seventy years was finally breaking down, and whether she was going senile at last.

"Mary?" she said as her secretary re-entered the room.

"Yes, ma'am?" said Mary.

Spithaler handed the parchment out to her. "Could you please tell me what this says?"

Mary frowned, took the parchment, and read aloud, "'For this year's Christmas Exchange, the Hogwarts faculty would be glad to receive the following: three pairs of knitted, woolen socks, five bottles of eucalyptus-scented bath gels, an ætites brooch, a seaweed strainer (underlined three times), a complete set of Battling Tops, two canisters of peppermint bark, and four quadrillion black balls with 8's on them.'" She blinked.

"Oh, good," said Spithaler. "I was worried for a moment."

"Four quadrillion black balls?" Mary repeated. "What on earth would anyone want with four quadrillion black balls?"

"Your guess is as good as mine, dear," said Spithaler.

"I mean, I knew the Hogwarts people were a bit odd," said Mary, "but which of them would be so cracked as to ask for something like this?"

"Well," said Spithaler reflectively, "we could possibly answer that question if we figured out who requested the other items. I know it's considered gauche to make two requests, so… could I see that list again?"

Mary handed the parchment back to her, and she passed her eyes over the first six items. "All right, let's see," she said. "The socks are Dumbledore's, of course…"

Mary frowned. "Are you sure?" she said. "I'll admit it sounds like him, but…"

"Certainly I'm sure," said Spithaler. "It's an old joke between the two of us: every year he asks for socks, and every year I send him books."

"Oh," said Mary. "Any particular reason?"

"Because I can't knit," said Spithaler, "and the old bumblebee knows it. Then, let's see, the strainer is Snape's; the peppermint bark is Flitwick's; the Battling Tops are probably for Charity Burbage in Muggle Studies…"

"Muggle Studies?" Mary repeated. "Hogwarts offers a class in Muggle Studies?"

"Sad, isn't it?" said Spithaler.

"Very," said Mary. "What about the bath gels?"

"I suspect those are Theano Vector's," said Spithaler. "She has a positive fetish for that sort of thing. And the brooch, of course, would be for poor Apollo Atrideug; aetites protects its owner against misfortune, which would be highly useful in his new job. So that leaves…" She paused, listing the remaining Hogwarts professors on her fingers. "That leaves McGonagall, Sprout, Binns, Sinistra, Tollers, Trelawney, and Kettleburn."

Mary snorted. "Sounds like a law firm," she said. "'Hello, you've reached the offices of McGonagall, Sprout, Binns, Sinistra, Tollers, Trelawney, and Kettleburn. At the sound of the tone, please describe the injury you gave yourself, the company you wish to sue, and the amount of your preferred settlement.'"

"Mm," said Spithaler, nodding vaguely. "Personally, I'd put my money on Trelawney. It's the sort of bizarre request she'd come up with."

"What does she teach?" Mary enquired.


"And what do the others teach? Sprout, Tollers, and the rest of them, I mean."

"Well, McGonagall teaches Transfiguration – what we would call Transmogrification," said Spithaler. "Then, let's see, Tollers teaches Ancient Runes; Binns teaches History of Magic; Sinistra teaches…"

"Wait a minute," said Mary. "There's a History of Magic course at Hogwarts?"

"Oh, certainly," said Spithaler. "That's one of the oldest courses there. Rowena Ravenclaw used to teach it."

"That's the one you want, then," said Mary positively. "That's the teacher who asked for the balls."

Spithaler blinked. "Binns?" she said. "What on Earth would Binns want with balls? I doubt the man's ever played a game in his life – or his afterlife, for that matter."

"He doesn't want the balls for themselves," said Mary. "He wants them as a gesture. Don't you remember telling me once about the Brickbracken Tax?"

Certainly Spithaler remembered. It was one of the more bizarre episodes in magical history: while George III had been inflicting his Stamp and Townshend Acts on the American colonies, his Minister of Magic, Fafnir Brickbracken, had, for reasons of his own, been forcing the enchanters of Virginia, Delaware and company to send him annual crates of Quidditch supplies. (This had not made the game popular in America, and it was this – along with the inordinate importance of the Seeker relative to the other players, which didn't sit well with the American democratic ethos – that had relegated Quidditch in the New World to the status of a novelty sport, played principally by the same sort of people as had made jousting the state sport of Maryland.)

"Of course," she said. "What about it?"

"Well, America hasn't paid the Brickbracken Tax since Brickbracken died in 1767," said Mary. "Maybe Binns decided to take advantage of the Christmas Exchange to collect 222 years worth of back taxes. Don't they use black balls in Quidditch, to knock people off their brooms or something?"

Spithaler considered that. On the surface, it sounded ridiculous – but not more so than the request. And it did sound like Binns, in a vague sort of way; it recalled his tendency to make remarks that sounded like jokes, but were so odd and unfunny that no-one could be entirely sure whether they were intended as such or not.

"What about the 8's?" she said. "What would those be for?"

Mary frowned, and thought for a moment. Then her face brightened. "Didn't Cricketshorn use to be in South Carolina?"

Spithaler nodded. "Up in a little cranny in the Appalachians," she said. "It was transplanted to the territories when the Civil War broke out."

"There you go, then," said Mary. "South Carolina was the eighth state to ratify the Constitution."

Spithaler frowned. "Do you think Binns knows that?"

Mary shrugged. "Probably he stumbled across some minor reference in one of his texts," she said. "You know: 'Shortly after South Carolina became the eighth state to ratify the Constitution, one of its Convention delegates paid a visit to his alma mater to welcome it into the United States', that kind of thing."

Spithaler hesitated. "There was an enchanter at the Convention, now that I think of it," she said. "I can't remember which state he was from, but…"

"There you go," said Mary. "And that's the sort of thing that would stand out to Binns, since most English enchanters don't even know who their Prime Minister is."

As a criticism of the British magical public at that moment, Spithaler wasn't sure this was quite fair; from what she had seen of John Major, indifference struck her as an eminently proper reaction to him. In a broader sense, however, she had to concede Mary's point.

"All right, then," she said, handing the list back to Mary. "Go tell Hoopy –" (this was how the Cricketshorn Charms mistress was universally known, silly nicknames being a distinguished school tradition) "–to pick up a box of bludgers from our friends in Oregon, and perform one of her famous Bottomless-Pit Spells on it. Procurement should be able to handle the other requests."

And thus it was that, on the morning of 25 December, Professor Herodotus Binns drifted through his door of his Hogwarts office to find a large, wooden crate awaiting him, which shook every now and then as though some object on the inside was striking its walls with considerable force.


"Ah, yes," Binns murmured to himself. "The Christmas Exchange, instituted in 1844 to solidify the historic ties between the wizarding populations of Great Britain and the United States." (He had an inveterate habit of showing off his own knowledge, even when there was no one around to show it off to.)

"Curious, though," he murmured. "I don't remember requesting anything. What could dear Miss Spellman have sent me?"

The crate made no reply, either to inform him of its contents or to remind him that the Cricketshorn headmistress's surname was Spithaler, not Spellman. It merely rattled again, and Binns began to vaguely appreciate that if he did not open his present soon, it might open itself for him.

Unfortunately, however, as a ghost, he was physically incapable of interacting with any object on the corporeal plane. He therefore summoned Hogwarts's caretaker, Argus Filch, and explained the situation to him. Filch listened thoughtfully, sneaking glances at the crate all the while, and it was not until Binns concluded his narrative that he spoke.

"So," he said. "You trust that thing, do you?"

Binns frowned. "Trust it?" he said. "What do you mean?"

"Begging your pardon, Professor," said Filch, "but if some American with a Cryotemp Jinx on her sent me a mysterious crate that shook every two seconds, I'd take it outside and throw it in the lake – and that's my advice to you, too."

"Nonsense, young man," said Binns severely. "I'm sure Miss Spader would never dream of using the Christmas Exchange as a subterfuge for nefarious activities. Now, then, go fetch a crowbar and open this crate, and look slippy about it."

Reluctantly, Filch did as he was told and left the office. He returned about ten minutes later, carrying a crowbar in his right hand – and, Binns noted with amusement, wearing one of the Great Hall's few un-enchanted suits of armour.

"It's all very well for you, Professor," he said with dignity as Binns let out a wheezing laugh, "but we flesh-and-blood people have to take a few precautions."

This said, he clattered over to the crate, wedged the crowbar beneath its lid, and pried it open.

–And the next thing he knew, he was sprawled flat on the floor, the crowbar knocked from his hand, watching Professor Binns scurry out of the room as 4,000,000,000,000,000,000 Bludgers with white 8's painted on them flew out of a 6'-by-3'-by-3' fruit crate and proceeded to wreak havoc on his office.

Filch attempted to sit up, but he was instantly struck by so many angry pieces of sporting equipment that he decided it wasn't really worth the trouble. He lay back down again and gave himself up to thought.

His first thought was that all his prejudices against Americans had been definitively vindicated. Any country where someone could have a propensity for sending unlimited numbers of enchanted, metallic, congenitally angry balls into a populated building, and still attain a position of high importance in the educational world, was a country that was every bit as crazy as he had always said it was – in fact, rather more so.

His second thought was even more gratifying. What exactly would happen when all these Bludgers left Professor Binns's office – as they were bound to do, once they finished beating down the door – and found people to attack who weren't dead or wearing armour? Of course, it was the Christmas holiday, so most of the students were safe – pity – but Peeves could always get knocked off, as could that great lummox Hagrid, as could – and this was the best part of all – one of those infuriating Weasley twins. And wouldn't that be poetic justice? The most skillful Beaters Gryffindor had seen in a century, bumped off by a swarm of rogue Bludgers.

Filch licked his lips beneath his visor – and then, suddenly, his expression changed from one of delight to one of utter horror.

For he had overlooked something. There was one completely innocent person at Hogwarts, and if Filch knew anything about magic, those Bludgers would go for her first. Madam Hooch could say what she liked about Bludgers being equalisers that were naturally attracted to the strongest players; in his experience, Bludgers liked an easy target as much as the next person – and what could be an easier target than an elderly, arthritic cat?

Filch pursed his lips. No, there was nothing else for it. Much as he would have liked to just lie there and wait for the Bludgers to demolish Hogwarts, for Mrs Norris's sake, he had to prevent them.

Of course, that was more easily said than done. How was he, a single, elderly Squib, supposed to overcome uncounted millions of Bludgers? Why, he would need… he would need… well, he wasn't quite sure what he would need, but he would certainly need something.

And then it came to him. Whenever he'd needed something in the past, there was a certain corridor that had always seemed to sprout a new room just for him. When he needed cleaning supplies, there was a closet full of Scouring Solution; when he needed a rock to throw at Peeves, there was a Hall of Geological Specimens. Well, right now he needed a way to get rid of a swarm of Bludgers; surely the corridor wouldn't fail him now.

Of course, there was the small fact that the corridor was on the seventh floor, and he was currently on the fourth. Still, if that was all that stood in his way, it could certainly be overcome.

And with that thought, Filch stiffened his shoulders, felt around and picked up his crowbar, and began to crawl on his belly towards the hole in the wall where the door had previously been.

About three-quarters of an hour later, a bright-red plume emerged from a secret panel on the seventh floor, to be shortly followed by an iron helmet, a suit of plate mail, and a string of rather colourful curses.

Argus Filch cannot truthfully be said to have been enjoying himself. He had hoped that taking the secret passageway instead of the stairs would have dissuaded those damned balls from following him, but it was not to be; when he had opened the fourth-floor entrance (behind the portrait of senmurves playing poker), about three hundred Bludgers had slipped in before he could close it again. His ears were ringing from all the times they had crashed into his armour, and that miserable white 8 had flashed past his eyes so often that he was sure it would haunt his dreams for a month.

He wondered idly whether that blasted infant Spithaler had even intended them to be 8's. He remembered Hippasus Pirr, the former Arithmancy teacher, telling him once that the Muggle symbol for infinity was an 8 flipped sideways; well, he had seen as many sideways 8's as he had right-side-up ones, and infinity certainly seemed like a more appropriate symbol for this insane offering.

Ah, well, it would be over soon. Filch glanced up at the extremely limited fraction of the wall that he could see, and – yes, there was the door, right where it was supposed to be. None of that song-and-dance about walking past it three times and focusing on your needs; evidently the room could appreciate a serious crisis when it saw one.

Of course, he wasn't quite sure how he was supposed to get the door open, since there was no way he could punch his arm through enough Bludgers to reach the doorknob – but when he crawled the last few feet to the far wall, he discovered that the thoughtful room had taken care of this problem as well. At the very bottom of the door, just at his current eye level, was a bright-red label: THIS DOOR IS VOICE-ACTIVATED. TO OPEN, PLEASE RECITE THE CURRENT PASSWORD OF THE GRYFFINDOR COMMON ROOM.

"Festal Menaion," said Filch. (As the caretaker, of course, he was always kept informed of the various common-room passwords – which, he reflected, was probably the idea.)

The door shuddered, hesitated for a moment as though unsure of itself, and then swung open. As it did so, Filch's eyes began to water, for the inside of the room was giving off an odour strong enough to be clearly olfactible at the other end of the school grounds; it smelled like the combined sweat, tears, energy drink, and used gym socks of every Quidditch player that ever sat on a Comet Two Sixty.

Instantly, every Bludger in the corridor stopped moving. The ones by the walls stopped smashing the picture frames, the ones by the ceiling stopped bashing against the chandeliers, the ones by the floor stopped crashing into Argus, and all of them began slowly bobbing in the air, as though drinking in the aroma of their natural prey.

Then, as with one accord, they darted toward the open door.

Within seconds, all 344 Bludgers that had come through the passageway with Filch had disappeared into the room, leaving Filch himself alone in the corridor. Shakily, he stood up, took a deep breath, and staggered over to the far wall.

"Quite something, that was," he muttered, and waved a hand against his face. "Phoof! Merlin's beard, what a stench! What's in this room, anyway?"

Curious, he twisted his head around and peeked through the doorway. Then he twisted his head back and shut his eyes tightly, but it was too late: one glance had been enough. Maybe the white 8's wouldn't be what haunted his dreams for the next month, after all.

There was nothing in the room. It was nothing but a pitch-black hole, with a series of white spikes girding the doorway and what looked uncomfortably like tonsils off in the distance. Filch had needed a way to get rid of the Bludgers, and the room had provided the most efficient and permanent way imaginable.

As Filch shuddered, he became aware of a low rumbling noise coming from the direction of the stairwell. He opened his eyes and turned to see the source of the sound – and then he dove backwards and pressed himself against the wall. This was wise, for in the next instant, the remaining 3,999,999,999,999,656 Bludgers flew past him and began to dive through the doorway, helpless to resist the lure of the weird room's maw.

Filch sighed in relief; the job was almost done. Any second now, the supply of Bludgers would peter out, and he would be free to go down to the hospital wing and see how many thorns in his flesh they had excised.

Any second now…

Any… second… now…

But the seconds passed into minutes, and still the black, metal river showed no signs of reaching its end. Filch was bewildered by this; he couldn't imagine why, at the speed these Bludgers were travelling, they shouldn't have long ago exhausted themselves.

Had Theano Vector been present to witness the scene, of course (instead of downstairs in her office, nursing a broken jaw), she would have instantly comprehended that it was a problem of ratios. A regulation Bludger is half a foot in diameter, which meant that the doorway, which was approximately 30" wide by 81" high, could accommodate 65 of them at any given moment. Furthermore, the Bludgers were travelling at a rate of about 1 mile per hour, which works out to 176 half-feet per minute. 65 times 176 gives 11,440 Bludgers entering the room every minute, and from there it is a simple matter of dividing 3,999,999,999,999,656 by 11,440 to conclude that, at that rate of speed, the last Bludger would enter the room in 349,650,349,650.35 minutes, or approximately half a million years.

Filch himself had never been very good at word problems, but after about fifteen minutes had elapsed, he began to get concerned. "You know," he whispered to the doorway, "it's very kind, what you're doing, but we need it finished by nightfall."

He had no clear conception of what he was asking. It was at that moment twenty minutes past eight in the morning, and, at Hogwarts's latitude, the sun sets at 3.42 p.m. on 25 December. This left 7 hours and 22 minutes for the remaining 3,999,999,999,826,924 Bludgers to enter the room, and, since the size of the doorway was relatively non-negotiable, the only way to achieve that would have been to increase the speed of the entering Bludgers to approximately 791,064,139 miles per hour, or about 1.18 times the speed of light – and it is, of course, scientifically impossible to accelerate anything past the speed of light in a finite universe.

But the Room of Requirement had been built to meet people's needs, not to pother itself about scientific possibility. It therefore instantly stepped up its pheromone production, opened its doorway as wide as it would go, and sent out several arcane spells invented by malcontented Pythagoreans, with the result that before Filch could enunciate the final L in "nightfall", the stream of Bludgers in front of him changed from a group of objects moving so fast that they could not be individually distinguished by the naked eye to a group of objects moving so fast that they could not even be meaningfully described in conventional language.

It was an event that any physicist in the world would have given his right eye to see, but Filch merely scooted up closer to the wall. If he hadn't wanted to get caught in the black swarm that he had hitherto been watching, he certainly didn't want to get caught in the not-quite-visible swarm that he was watching now; he didn't know, precisely, what would happen to someone who stepped into that mind-bending stream, but he was quite certain that it would not be healthy.

So he stood stock-still, and, for a while, the only sounds that could be heard on the seventh-floor corridor were the whooshing of air displaced by the Bludgers and the regular sonic booms essaying from Professor Binns's office. After about twelve minutes, however, Filch heard a new, and completely unexpected, sound: footsteps. Someone was heading towards him.

Puzzled, he inched over to the corner of the wall and peeked around, wondering who could have been so mad as to have been voluntarily entering the corridor at that moment – and then his eyes beheld a most astonishing thing. Professor Apollo Atrideug was coming up the seventh-floor staircase – walking in the very midst of the river of Bludgers.

And the Bludgers were not harming him. In fact, as far as Filch could make them out, they appeared to be actually swerving around him, as though they had been given strict orders not to harm the Defence against the Dark Arts professor – which was ridiculous. Defence against the Dark Arts professors, at least at Hogwarts, were there to be harmed.

As Filch goggled at this wondrous progeny, his armour clanked against the wall, and Professor Atrideug glanced up at him. "Ah, Argus," he said. "So you're the one who caused this bizarre phenomenon, are you?"

"Eh?" said Filch.

"Here I am," said Atrideug, "sitting peacefully in my office, and all of a sudden a crowd of Bludgers beats down my door and starts smashing the room to bits. Then, suddenly, an incredible stink of sweat hits my nose, and every ball Jack of them stops moving for a moment and then flies back out the door. Naturally, after I've straightened the place up a bit, I take a look outside, and I find this current of I-don't-know-what zooming up the stairs at incredible speeds. I go to follow it, and whom should I find but you, sporting a suit of plate mail and standing next to the doorway through which all these super-accelerated Bludgers are racing like there's no tomorrow?" He waggled his finger at the caretaker. "Highly suspicious, Argus, highly suspicious."

"Uh," said Filch intelligently.

"So what's the secret of this wonderful doorway, anyway?" said Atrideug. He walked over to the room and glanced inside, and his lip curled in distaste. "H'm," he said. "Not exactly what I'd pick for a Christmas vacation. You?"

Filch shook his head dumbly.

"Still, it's a mighty clever trick," said Atrideug. "I didn't know there were such things as predatory rooms, but if you are one, that's definitely the way to go. Make yourself seem like the most delightful thing your prey can imagine, get it speeding into your mouth as fast as it can go, and then – slu-u-u-u-urp!" He shook his head. "Reminds me of that shadhavar I tangled with in Afghanistan – except in his case it was sound, not smell…"

"How are you doing that?" Filch interrupted, his brain having reacquired sufficient potency to form that sentence.

Atrideug blinked. "Doing what?"

Then he glanced down at the stream of crazed Bludgers that was scrupulously avoiding contact with him, and chuckled. "Oh, that," he said. "That's due to this little fellow here." He popped a brooch encrusted with a shiny, grey stone off his lapel and held it up for Filch to observe.

"Ætites," he said. "Spithaler's little Yuletide gift to yours truly. Protects its bearer from all harm; rather convenient, especially in a high-risk job like I've got. Of course, some poor eagle has to be rendered infertile in order to get it – but then, that's the proud, mad war of Nature for you, now isn't it?" And he tossed the brooch jauntily in the air.

And that was his undoing, for while ætites does indeed protect its bearer from all harm, anyone who tosses it in the air has, for a brief instant, ceased to be its bearer. There are therefore many situations in which this is an unwise thing to do, but perhaps the worst is when one is standing in the middle of a stream of Bludgers travelling toward certain doom at 1.18 times the speed of light.

It happened so quickly that Filch was unable to completely process it. One moment Professor Atrideug was there; then there was a brief crunching sound, and suddenly he wasn't anymore. Since he was travelling so much faster than the speed of sound, it was a number of minutes before Filch even heard him scream.

On some level, Filch was sorry to see him go like that. He had been one of the better Defence against the Dark Arts teachers, and it would have been nice if he could have just resigned or been abducted or something – and it was certainly a shame that that poor eagle had sacrificed her fertility to no purpose. Still, that was the business, and it was no use getting all sentimental about it.

"That's it, then," he muttered to himself. "Hogwarts DDA bags another one." And with that, he dismissed it from his mind, settled back into his former position, and waited for the end.

It came, as has been foreshadowed, at 3.42 p.m., just as the last rays of the setting sun were seeping through the castle windows, casting a golden sheen on everything within (except the Bludgers, of course, which they weren't fast enough to strike). Argus Filch, who by this point had missed two meals, had been standing for over seven hours, and was becoming extremely weak, hungry, tired, and cranky, barely noticed as the last row of Bludgers swooped past him and into the room; it was only when the air that they had been displacing flowed gratefully back into its regular current that the cold blast and loud whoosh alerted him to his newly regained liberty of movement.

Heaving an enormous sigh, he slumped down onto the floor and began removing his armour, piece by piece. He had just managed to work the helmet off his head when a new, heavier set of footsteps sounded on the stairs, and Hagrid poked his head around the corner. "There yeh are, Filch," he said. "Been lookin' all over for yeh."

Filch groaned. "Hagrid," he said, "do me a favour and go jump in the lake."

Hagrid frowned. "Well, all righ'," he said. "Don' s'pose I c'n begrudge yeh that – but I thought yeh might like ter know that someone else's been lookin' for yeh, too." He parted his legs, and a lanky, grey tabby cat darted out from behind him and into Filch's lap.

Filch's eyes widened. "Mrs Norris…" he whispered.

"Foun' her curled up near the trunk of the Whompin' Willow," said Hagrid, and chuckled. "Clever little critter, ain't she? Imagine all them Bludgers tryin' to get a crack at her, and the Willow just bashin' 'em away from her."

Filch barely heard him. As Mrs Norris curled up in his lap and nuzzled at his breastplate, all the worry, annoyance, fatigue, and trauma he had experienced over the last seven hours came bursting out of him in one emotional maelstrom, and he held her in his arms and sobbed like a baby.

When Hagrid saw this, his sentimental heart was deeply moved, and in a spirit of brotherly commiseration he picked Filch up and enfolded him in an enormous bear hug. It was a tender and private moment, unobserved by any save Mrs Norris and the Room of Requirement, neither of whom had any intention of telling.

(Although the Room eventually did so in 1999, when Ginny Weasley needed a photograph wherewith to blackmail the Hogwarts caretaker.)

The rest of the story may be told briefly.

Injuries from the Bludgers were surprisingly low. Apart from Atrideug and Vector, the only faculty member who was seriously injured was Severus Snape, who was struck violently on the head and laid up in the hospital wing for two weeks. (He was more annoyed, however, by the fact that his seaweed strainer had been smashed into an unrecognisable lump of metal.) The only student who spent any time in the hospital wing was Fred Weasley, who made the mistake of trying to sneak up behind a Bludger with his Beater's bat just as it bolted for the seventh floor.

On 26 December, Albus Dumbledore paid a visit to Cricketshorn and had a lengthy discussion with Headmistress Spithaler, which ended in the two of them both laughing uproariously and trading bad jokes about Magic 8 Balls.

Filch never told anyone about the Room of Requirement, so no-one ever learned what had happened to Apollo Atrideug. For the duration of the spring term, Defence against the Dark Arts was taught at Hogwarts by a number of unofficial substitutes, including Severus Snape and a rather timid gentleman named Phobos Quirrell.

The Weasley twins, along with all the other students who had stayed at Hogwarts for the holidays, fully expected the story of the Great Bludger Attack to become part of the tissue of school legends, but there are some things even Hogwarts students won't believe. After about a week of trying to convince their peers that Professor Binns had really received a bottomless crate full of graffitoed Bludgers as a Christmas present, they finally gave up and never mentioned it again.

Minerva McGonagall never did get her billiard balls, and her sixth-year students wound up having to make coal out of black licorice.

When Christmas of 1991 rolled around, Professor Binns was assigned to write the request list, and every member of the faculty took time out from his or her schedule to pray that the Exchange would go more smoothly this year.

It didn't.

But that is a story for another time.