Author's note: I'm certain some variation of this concept has been done before, but hopefully at least the story itself will be original enough to please.

This story is AU, replacing the events in Half-Blood Prince and Deathly Hallows. I will make reference to items, events and concepts that came up in Half-Blood Prince and Deathly Hallows – they will be altered to fit into this new storyline, but there are still possible spoilers.

"Snape" is usually used to refer to Professor Snape, and "Severus" is usually used to refer to student Snape.

This story has been a long time in the making, since it was started in 2007, finished in late 2009, but not revised and posted until 2011.

Chapter One

He glided up the aisle with scarcely a noise, his robes making a soft whispering sound as they brushed by the desks. "Two minutes remaining," he murmured in a threatening baritone. Most of the students had not completed their potions, and he allowed himself a private smirk as he watched them scramble to finish on time.

His smirk turned to a sneer of disgust as he caught sight of three heads (one dark-haired, one flame-colored, and one a tousled mess of chestnut curls) bent over a cauldron. He had no real objections to having Granger in his Advanced Potions class, though she was an insufferable know-it-all. However, Potter and Weasley had only received E's in their potion OWLS (privately, he was gobsmacked that they had managed to do even that much) and had no right to even sit in the presence of Outstanding students. But of course the Boy-Who-Lived-to-Be-A-Brat must be coddled and carried along the way to whatever glorious fate awaited after the impending defeat of the Dark Lord, Merlin willing.

It had taken a good deal of wheedling and arm-twisting, with a smidgen of old-fashioned blackmail for good measure, for Snape to relent on his policy of O students only. He was positive that Dumbledore had been a Slytherin in a previous lifetime. He was a bit awed, in spite of his outrage.

"Time's up. Please bring your cauldrons to the front of the room for inspection."

Potter stood up, cauldron full of simmering potion in hand. Today, with an inward shudder of apprehension, he had allowed the students to select which NEWT-level potion they had wanted to brew. The Gryffindor trio-of-doom had brewed a Separating Solution, which was useful for separating potions into their base compounds. Draco and his cronies had created a Youth Serum.

Severus was heading to his desk when a scuffle caught his attention. As usual, the Potter brat was at odds with Malfoy. Malfoy gestured with his wand, causing Potter to trip and spill the contents of his cauldron. The Slytherins snickered. In retaliation, Weasley fired off some kind of hex, causing Malfoy's cauldron to send a geyser of potion rushing out. Both concoctions hit the unfortunate Potions professor within seconds.

Snape froze and remained stock-still. A most unpleasant sensation was nagging at him – it began as fingers tickling his back but quickly mutated. He tried to lunge for the emergency shower, but as he turned he felt a tugging sensation, much like a rubber band that had reached its stretching limit. He bit his lip against a cry of pain and tasted blood. Just as the pain reached its crescendo, it abruptly cut off.

The Potions master stood shuddering and gasping, almost in shock. The infernal children stared at him in mute horror. It gave him some grim satisfaction. Yes, they lived in fear for what he would do next… would he scream and fly into a rage, or would his voice become deathly quiet as he flayed the skin from their bones with his barbed tongue? Then he realized that their gazes were focused somewhere behind him. With a sense of trepidation, he turned.

There was a student behind him. A Slytherin, judging from his robes. But this was no student that he recognized. The boy raised his head, and Snape felt a jolt.

Snape blinked his black eyes. The boy blinked equally black eyes in response. "Who are you?" the professor said slowly, already suspecting the response.

The student frowned. "I was just about to ask you the same thing."

There were a few soft gasps. The boy's voice was higher, but there was no doubting that the two voices were remarkably similar.

Snape studied the boy. He was tall and skinny, bordering on bony. He had a waxy, sallow complexion. His hair was black and hung almost to his rounded shoulders. The strands were lank and greasy-looking. The man groaned in despair. "Severus?"

"Yes," the boy replied warily.

Hermione sensibly decided to act. "I'll go fetch Madame Pomfrey."

Snape still appeared in shock. "Better inform Dumbledore as well."