Chapter One

"POTTER!!" barked Snape, rushing towards Harry's desk, his cloak billowing out behind him. He slammed both his hands on Harry's small desk, and peered into his simmering cauldron. Harry sat as still as stone, feeling the stares of everyone around him on the back of his head.

"What's Potter done now?" sneered Draco, nudging Crabbe and Goyle, snickering and mimicking Harry's frozen stance. Parvati Patel let out a shriek of laughter which echoed off the stone walls, resonating loudly in Harry's ears.

"Potter," said Snape dangerously, "do you know what you have just done?" he looked into Harry's blank green eyes, and stood up triumphiantly. "Potter has just displayed an act of pure genius" he announced to the class, "Pure, idiotic genius. Since when do you mix Mandrake root with Unicorn hair if you haven't added-"

"Juice of Burnybean" Hermione whispered, groaning. "Harry, how could you have forgotten that? It's written on the board!" she whispered quickly.

"I think you should come and see me in detention on monday for this mistake, Potter. You can tidy up the store cupboard as you have wasted so much of my time and my efforts" Snape said harshly, spraying Harry's cheeks with flecks of spit. Without another word he wiped Harry's cauldron clean, and turned around quickly, brushing Harry's hand with his cloak. Harry gripped the sides of this cauldron tightly, his hands slowly turning white, muttering darkly. Hermione quietly loosened Harry's grip on the cauldron, and gave him a small flask.

"Here, drink this" she said, "I made it last lesson, it's a potion which cheers you up. Very tricky to make, but I think I got it right. It lasts for about a day, depending on how annoyed or upset you are". Harry took the small silver bottle, uncorcked it and downed it in one go.

"This had better not be anything bad, Hermione" he whispered, and suddenly froze at the look of terror on her face.

"Oh no" she breathed, and she took out a similar silver bottle. "Harry! Spit it out!" She grabbed his neck and flung him around, but Harry only gasped and prised her fingers away.

"Hermione! What are you playing at?" he croacked, rubbing his neck, "what did you just give me? I thought you-" he stopped, mid sentence, and suddenly felt a ripple of cold air go down his spine. His skin over his fingers started vibrating, started moulding into something else, the bones on his arms started to shrink to a smaller size, and he felt his hair on his head become thicker. He looked down at his legs and almost jumped out of his skin, they had become longer and ganglier. "Give me a mirror" he whispered at Hermione. She buried herself in her bag and produced a hand mirror. Harry took it quickly, and what he saw nearly made him scream.

"Harry, I'm so sorry!!" Hermione moaned, "I didn't realise. I was saving this for Malfoy, I forgot I still had it in my pocket!" Harry ignored her, staring at his reflection. The face which stared back out of the mirror was not Harry, but a younger, much younger version of Severus Snape.

"Hey Harry, don't worry about the potio-" Ron started saying, turning towards Harry. He caught sight of his face and yelped loudly, crashing his arm backwards into his cauldron, spilling its warm contents all over the floor.

"WEASELY!" barked Snape, "WHAT HAVE YOU-" he stopped. He stared at Harry, his eyes widening in shock. The whole class fell silent as Snape walked slowly towards their bench, his eyes filled with fury, his face turning white and his mouth beginning to shake. He prised open the empty silver flask which had contained the potion and sniffed it, his long beaky nose hovering over its mouth.

"Shape shifter potion. Become your worst enemy for a week, retain only your origional eye colour" he whispered. "I suppose this is Granger's doing." he stared at Hermione, who had her head bent down meekly and whose cheeks were beginning to flush pink. "Well Potter, I am honoured that I am your worst enemy. I hope you do enjoy this week, I will still be expecting you in detention." He turned away and called out loudly "would the rest of you bring me a sample of your potion. I will be expecting your essays on the use of..." Harry cupped his hands over his ears and groaned quietly. How could this happen to me? He thought miserably, and he looked into the mirror again, staring at the pale faced, green eyed youth who was looking out at him.

Ron was still staring at Harry, a smile beginning to etch on his face. Harry turned towards him, and before he could open his mouth to say something Ron burst out laughing. Everyone was craning around to stare at Harry, and were whispering loudly. Parvati Patel stared at Harry, her mouth lopsided, her head tilted to one side, trying to figure out if it was an imposter or if it was really Harry.

"Can we get out of here?" Harry whispered, and quickly packed his bags with his books, trying to shield his face with his cloak but only succeeding in knocking his quill over. Ink splattered his face and his hands, and as he tried to mop it up he felt Hermione shaking with laughter beside him.

"What!" he snapped angrily, "this wouldn't have happened at all if you hadn't given me the potion!"

"Nothing-" Hermione said through broken laughs, "just that now, you- you suit the p-p-art of Snape even better!" she said, tears forming at her eyes, her whole body shaking with silent laughter. Harry turned away from her, picked up his bag and stormed out of the classroom, not caring if he was called back in.

"Bye Severus! See you later!" people chanted at Harry on his way out. He ignored them, and hurried out of the dungeons.