Believing is Seeing by LBibliophile

Severus growls to himself as he watches the new fourth year students scurry to gather their potion ingredients. What is it with the Headmaster and his idiotic insistence on pairing the Slytherin and Gryffindor students? Especially in his class! Really; the one subject more than any other where inattention and mistakes – not to mention active sabotage – can be catastrophic. Keeping an eye on his first year students earlier in the week was bad enough, but this class, with Potter and –

"Longbottom!"

Eyes across the classroom snap to look at him while the Gryffindor boy jumps, dropping the entire handful of malachite – crushed, not powdered, he notes – into his cauldron. Severus waves his hand, wandlessly extinguishing the fire underneath but it is already too late. Even as he strides across the classroom, the potion is bubbling and foaming, turning a dangerous green. The Potter boy looks back down at the cauldron he had been stirring moments before just as the potion erupts, surging upward and drenching his arm. Vanishing the ruined potion before it can do any further damage Severus comes to a stop in front of the two Gryffindors.

"Potter, give me your arm."

The stubborn boy just pulls away, frowning. "I'm fine. It's nothing."

Severus doesn't say anything, but his glare shouts louder than words. Am I the Potions Master here or not? Without giving the boy a chance to protest further his hand lashes out to grab his wrist, holding it firmly despite the boy's violent flinch. Dragging Potter's arm towards him he pushes the now-dry sleeve aside to inspect the damage.

He stares. Potter's arm is before him, smooth and unblemished, no sign of a potion burn marring his pale skin. It's not possible. Longbottom, despite his impressive record, is hardly the first student to cause such an explosion, nor is Potter the first to be caught in one. He knows what he should be seeing.

He blinks, and suddenly the burn is there, red and angry across the inside of the child's arm. But this view is no more possible than the last. Where previously the skin was pale, now it is mottled sickly green and yellow, interspersed with patches of livid purple. The sight is not unfamiliar – nor the feel for that matter – but not on perfect Potter!

He blinks again and his racing heartbeat slows. This is what he is supposed to see. Yes: potion burn. No: unsettling bruises. He really must double check the potion ingredients he allows students to use; he can't afford to have fumes giving him hallucinations like that.

Realising he is still holding Potter's wrist, he quickly pulls a jar of cream out of his pocket and spreads it thickly over the burn, dropping the arm as soon as he is done.

"Potter, the cream should counter any magical effects of your foolish accident. Pack up your things and see Madam Pomfrey for the burn. Longbottom," he turns and sneers at the trembling boy standing next to his half-melted cauldron, the familiar action calming him further. "Clean your area; you have once again managed to earn yourself a zero for today's work. You may then spend the rest of the lesson rereading the chapter in the textbook, since it obviously failed to penetrate your thick skull the first time. Ten points from Gryffindor for disturbing the class."

"As for everyone else," his eyes rake across the watching students around the rest of the classroom, "your potions should be at a rather delicate stage at this point. Unless you wish to join misters Longbottom or Potter, you would be advised to attend to them."

Severus stalks back to his desk as the room bursts into motion. He doesn't like this. His instincts are telling him something that his mind says can't possibly be true. Yet he hasn't survived for so long as either a teacher or spy without trusting those instincts. He knows what he would do if it was one of his snakes, but… Potter? Surely not.

He scowls as he watches the boy quickly gather his books. He knows that there is something wrong. It is just possible that he is mistaken about the bruises he thought he saw, but combined with their meeting in the corridor two days ago, and all the little clues he has noted subconsciously over the years… He makes a decision.

"Potter." His voice snaps out across the room, stopping the boy in the doorway. "Tell Madam Pomfrey to give you my special diagnostic." He sneers. "Given Longbottom was involved, one can only imagine just what side effects might manifest. And it would never do for something to… inconvenience… the precious Boy-Who-Lived."

Potter nods curtly and leaves, and Severus can only hope that he will obey his least favourite teacher's orders. He supresses a sigh. It is done; Poppy will know what to look for. If his instincts are wrong, Potter will never know about his suspicions. If they are right…