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

Warning! This story is rated 'M' and is identified as both 'horror' and 'tragedy'.

Note: This story is set in an alternate universe. It's possible that some characters behave in ways in which (even under the different circumstances) their canon counterparts would not, but this is an alternate universe, and I'm not J. K. Rowling.

By the time that the infiltration of Hogwarts had been conclusively brought to light in late February of 1978, it had been far too late to prevent the damage that would inevitably come. Gryffindor house descended into chaos, friend turned against former friend, and by the time that the morning of February the 24th finally dawned, there was a trail of bodies of teachers and of pupils – and the head-boy had slipped the pursuit and escaped the school to go and take his place at Voldemort's side.

Albus Dumbledore tried to catalogue the damage, but the cost almost made him weep. At least a dozen Gryffindor pupils had absconded with their idol Potter and his infernal mistress, along with several Ravenclaws and Hufflepuffs. It was possible that the corruption had spread still further, and that Potter had left behind spies and sleeper-agents, as yet undetected, in the school.

Albus supposed that the first 'werewolf incident' was perhaps the last and only moment where he might have glimpsed the shadows of what was to come and perhaps averted this crisis – the occasion when Potter claimed that Severus Snape owed him a debt for Potter's 'saving' him from an attempted murder in which Potter had gotten cold-feet at the last minute. At the time Albus had regrettably considered the event merely the results of house rivalry gone slightly too far and of overly-high spirits – and in any case more of a problem regarding Mr. Sirius Black than Mr. James Potter. Sadly it was now all too clear that overlooking Mr. Potter's part in proceedings had turned out to be a mistake. Potter had learned from the incident – and although well over a year had elapsed after that first occasion without further trouble occurring involving Remus Lupin, Potter had eventually taken up again where he and Sirius had originally left off. In the past six months Potter and his new partner-in-crime had orchestrated a string of further 'werewolf incidents', in which Potter had abused his unwitting friends to snare at least half a dozen other souls in his webs of treachery and deceit. Whilst Mr. Snape had never held himself to be in Potter's debt on the grounds that Potter and his friends had setup his near-death encounter, other pupils had apparently proven much more susceptible to Potter's spurious claims of life debts. And in one final ironic twist, Snape had been killed this very night, protecting Sirius Black from a rampaging werewolf, from James Potter, and from Potter's demonic paramour.

'Cathy Shields' – she had seemed so innocent, back in September, claiming to be a seventeen year-old transfer student, from Salem, in the USA, and with impeccable credentials to back her story. Albus now suspected that she had met Potter over the summer holiday of last year, before even arriving at Hogwarts. When Potter turned up in September for the start of this school year and to take up the position of head-boy he had shown no signs at all of the interest in the head-girl, Lily Evans, which he had displayed in previous school years – but right from the word go he had flirted with the false American outrageously. Ms. Shields, in public, had played the part of a quiet, shy, retiring young lady, who absolutely adored those who excelled at quidditch – and James Potter in particular. She had had half the boys in the upper two years pursuing her, and she had pretended to be quite flustered by all the attention. In private, in several of the hidden rooms about the school, it had been another matter altogether, Albus was now learning, with Ms. Shields and Mr. Potter presiding over a number of thoroughly debauched orgies and ceremonies involving the darkest possible magics. Muggles had been smuggled into Hogwarts by Potter, with the assistance of his invisibility cloak, for blood-sacrifice purposes. There was evidence which seemed to indicate that at Ms. Shield's encouragement Potter and at least one Ravenclaw student may have each manufactured for themselves a horcrux. It seemed that they had considered no atrocity too dark to commit, and only the logistics of trying to maintain secrecy in the school may have kept their activities at least partially in check.

Severus Snape, always paranoid and suspicious of Potter, had unearthed what Potter had been able to keep from his former closest friends, Peter Pettigrew, Sirius Black, and Remus Lupin. Albus wasn't quite sure why Potter apparently hadn't tried to approach and corrupt his fellow 'Marauders' – maybe he'd thought that they couldn't keep a secret, and had intended to approach them later, once they were all done with Hogwarts, or maybe he'd considered them unfit for his purposes – but if he hadn't approached them, then neither had they had any idea what was going on under their noses. Nor had the head-girl, Lily Evans, who had snootily ignored Severus Snape and his warnings that there was something very wrong in Gryffindor Tower, though the head-girl was devastated now. At the height of last-night's battle James Potter had offered Snape 'everything you could ever want, including Evans', if he switched sides and offered his wand to serve Potter and the Dark Lord. Snape had sneeringly declined, saying he would never want Evans as a drooling slave to an Unforgiveable, and that she had made it quite clear that that was the only way he could have her. Several minutes later Snape had stepped in front of a dark curse intended for Sirius Black, who was fighting his former friend, Potter, in horror at what he had become – saving Black, but taking a mortal wound. Snape had died messily moments later, his last words being 'fight on you idiot, gawp about me if you must, afterwards'.

Despite the horrible cost in lives lost and innocent souls corrupted, at least there were some bright things in all of this. Some of the old pure-blood families – especially Slytherin ones – who had been prepared to formerly tacitly support Lord Voldemort were now hurriedly distancing themselves from the Dark Lord. There were some forms of magic too dark for even their liking, including that which must have created the abomination which Dumbledore now recognised as having infiltrated the school in the guise of Ms. Shields: a succubus, spawned of the blackest of magic and a veela, she had unparalleled powers to tempt and corrupt adults of either sex, and from what Albus recalled reading of the inception and loyalties of such creatures her presence indicated Voldemort must have been planning and readying himself for this war for at least the decade prior to the seventies. It was some small consolation that she was now finally out in the open, where the wise heads of some of the country's oldest families could see what she could mean for institutions which valued family bonds and loyalty above all else.

She had caused untold devastation at Hogwarts as it was, and helped to seduce to the Dark Lord's side some of the best and brightest young minds of a generation. Albus could only hope that her exposure might have at least cost Voldemort some of his more traditional support to offset these losses…

Author Notes:

This piece originated as an attempt to write a piece where the Marauders spectacularly fall apart during their last year at Hogwarts, and an over-the-top overtly 'bad boy' James Potter seemed the way to go…

Evil villains sending beautiful women in to seduce their enemies is a staple in some forms of fiction (sometimes it works, sometimes it backfires spectacularly), and James Potter (quidditch idol, golden boy of Albus Dumbledore, and mischief-maker of Gryffindor) seemed to me a credible target to have a temptress pointed in his direction by Voldemort.

The Albus Dumbledore of this particular alternate universe is over-reaching, somewhat, when he imagines that signs were there of what was to come during this universe's 'original' werewolf incident (which probably happened at some point during 1975, which may differ from canon). It was meeting Voldemort's agent during the summer of 1977, which tipped this version of James over the edge. She played up to his ego with gratuitous amounts of flattery, and seduced and damned him.

For the purposes of this universe, James Potter and/or his paramour have some form of dark magic which can enslave Remus Lupin to their wills when Remus is transformed into a werewolf. Possibly they can use it to keep him transformed at times even when the full moon isn't in the sky.

Severus Snape threw himself in front of a curse meant for Sirius Black because it was the only way out he could see for himself. He wasn't going to work for Dumbledore, given the previous six and a half years in Hogwarts, and now, with James Potter all set to become one of Voldemort's chief lieutenants, there was no way he was going to work for Voldemort either, if it meant having to look up at James Potter lording it over him every day. Rejected by Lily, all he wanted was to die… being able to do so in a way that would have the potential to make Sirius Black squirm uncomfortably for the rest of his life (Black having been saved by his enemy 'Snivellus' from two of Black's own 'friends') was about the best way that he could think of to go.

With regard to the aftermath of this story, I'm not sure of much which would happen, but I think Peter Pettigrew would end up being a confirmed good-guy and marrying Lily. (They might even call their first-born Harry Severus Pettigrew, out of a belief that Severus was being heroic that night he saved Sirius.) Sirius (likely accepted back into the bosom of his family if they decide to hurriedly distance themselves from Voldemort) would end up much too busy with tracking down his once best mate, James, who betrayed him and who's enslaved Moony, to bother with things like romance.

This story is a one-shot.