Harry Potter walks into the Great Hall, and your breath disappears.
It's like watching his father stride into the room all those years ago, and for a second you're arrested by the hatred of a memory. The boy glances around, catches the full brunt of your glare and looks away, leaving you gasping with indignation at his casual indifference. A chip off the old block, then.
He's sorted into Gryffindor, of course, and as you watch him being cheered towards his new housemates, you vow that you'll show him he's not everybody's darling, whatever he may have been brought up to believe.
In your first lesson with Potter, you are taken aback to discover that his eyes are not hazel but green. The dark, earthy colour tugs at your memories, and you're grateful that it's effectively obscured by those ridiculous spectacles.
You redouble your efforts to put him in his place, infuriated that he appears more confused than humiliated by your onslaught. You leave the lesson angrier than ever: even at eleven, this boy reminds you of everything you dislike about yourself.
Potter turns out to have a hero complex, and you're not sure whether to be pleased or insulted when you learn that he and his cohorts had believed you were after the Philosopher's Stone. You consider pointing out to him that you could have plucked the Stone from its hiding place at any time during the past nine months, but decide that you don't care what the imbecile thinks of you anyway.
One year down, six to go.
What begins as an exercise in belittling Potter bears unexpected results when he is revealed as a Parselmouth. You take perverse pleasure in watching the rumours and paranoia spreading almost instantly; it's a small revenge for the petty humiliations you've nursed for fifteen years.
You know perfectly well who opened the Chamber of Secrets fifty years ago, and you've been trying very hard not to think through the implications of the disturbing events that have been disseminating terror throughout the school. The old scar on your arm itches, but then it always has done. No change there.
The Parselmouth issue is interesting, though. You begin wondering exactly what happened to Potter when the Dark Lord fell. Is that scar on his forehead more than a mere war wound? You know that Albus, with his laissez-faire attitude, will never contemplate this, but you resolve to watch Potter more carefully than ever. You knew the Dark Lord, after all: who better to identify potential successors?
In the end, it's a silly little girl causing the trouble. Potter charges to the rescue once more, and once more he's feted by Albus and the rest of the staff. Who would have thought a twelve year old boy could achieve so much? Minerva enthuses with tears in her eyes. You roll your eyes and promise yourself that one of these days you'll expose Potter for the charlatan he is.
With Potter causing trouble in lessons, Lupin antagonising you in the staffroom and Black closing in upon Hogwarts, you sometimes feel as if you're sixteen again. You remind yourself that the dynamics have changed: Black is a fugitive, Lupin a broken man with a secret and Potter a mere boy, while you hold true authority now.
You refuse to believe Lupin wouldn't help his old friend, and so you watch him and you wait. When it happens, though, it's over almost before it began. One second you're a hero, the next Potter has somehow confounded everyone and helped Black escape. The fact that you manage to get rid of Lupin is scant comfort, and you can barely restrain yourself from cursing Potter when you pass him in the corridors.
The next year, you have bigger things to worry about than Potter, although inevitably he comes into it in the end. The brand on your arm, which has never truly stopped prickling, is burning as intensely as it ever did, erasing the past fourteen years in an instant. You've always known that this might happen, and so you do what you have to do, and try not to contemplate the probable results of failure.
You shake hands with Black under duress; you know better than most what his mercurial charm can do, and you promise yourself that you'll have revenge for your purgatorial schooldays at his and Potter's hands.
Albus may be busy, but you find it difficult to believe that he truly thinks you're the best person to teach Potter Occlumency. You attempt the task without enthusiasm, and are unsurprised to find that Potter becomes more obtuse and obnoxious every week.
You walk into the dungeon one evening and find him raking through memories that you'd rather have died than reveal. For a moment, it's gratifying to finally let fly at Potter – it's the confrontation you never had with his father – but you soon realise that the humiliation of knowing what he's seen outweighs any satisfaction that you're getting from lashing out at him. You banish him from your sight and from Occlumency, and you hope, for one bitter moment, that the Dark Lord's plan comes to fruition.
How ironic that you're finally teaching your preferred subject at a time when your options appear to be closing in around you. You spend your classes drumming defensive practices into your students, and your leisure time formulating hopeless plans for every eventuality.
Potter has inexplicably become a genius at Potions, it seems, although it isn't until he uses one of your nastier spells on Draco that you understand where his newfound knowledge originates. The boy appears to be amazingly dim when it comes to identifying his de facto partner in crime, however, and you wonder again just how much of his apparent intelligence is the result of his friendship with Hermione Granger.
How can two words hold such power? You have to mean these things, and so for a moment you concentrate on all the injuries you've ever borne on Albus's behalf, before flinging the spell at him with such ferocity that his body sails over the parapet and down into the darkness.
That task complete, you concentrate on the next one: extricating Draco from the castle unscathed. You note his wan face and hope that this fiasco has taught him a lesson, albeit belatedly. But perhaps it has always been too late for you and Draco.
Potter is screaming at you, flinging hexes your way and becoming infuriated as you effortlessly deflect them. It's only when he calls you a coward that you lose your temper, because you know that coward is the one thing you are not, and you also know that your troubles are only beginning. You throw him to the ground and begin to run, only to hear screams behind you: some bloodthirsty idiot has cast the Cruciatus curse on the boy. You end the spell, remind the others that Potter is not to be touched, and then you run again. And run. And run.
You know you don't have long, but you think you'll be safe here tonight. They'll be too busy reeling from Albus's death to look for a Death Eater in a poky Muggle terrace at the top of a Lancashire mill town. You've left Draco, pale and terrified, asleep in your bed; you're being kind to him, because you know the Dark Lord won't be, but it's an effort after all he's done, and you've come down here to think.
You poke at the fire as you make your plans. You know you'll have to return to the Dark Lord tomorrow, taking Draco with you. Voldemort will be pleased with your work, and perhaps you can intercede for the boy. It's the only way.
You remember a boy, thin, with messy hair and glasses. And just for a moment, you wish that things could have been different.