Both wizards were looking at Harry appraisingly. Gasping, Harry struggled to keep the tremors out of his muscles.

“Control yourself, Potter!” snarled Snape. Harry’s head shot up from his arms and he fixed Snape with a glare. Snape returned the glare with equal-perhaps greater-contempt. His lower lip curled into a sneer. Harry shook with inexplicable rage.

“What’s—what’s wrong with me?” he bit out. He looked between Snape and Dumbledore for nonverbal answers, but neither man was giving anything away in his expression.

Finally, Dumbledore held up a hand in acquiescence.

“It seems we have much to discuss, Harry. But first, Severus, if you please—” Dumbledore began. Snape nodded sharply and silently Summoned another small vial. He caught it in between his thumb and his index finger.

"This, Potter, is a—Pepperup of sorts—it’s my own creation,” said Snape, his countenance proud but inscrutable. Harry could barely hear him over the sound of blood rushing through his ears. Dumbledore reached an arm out as though he wanted to put a hand on Harry’s shoulder, but Snape telegraphed what he thought of this idea with narrowed eyes and a clenched jaw.

Dumbledore slowly drew back his hand.

“Take it,” Snape said, indicating the vial with a decisive flick of his wrist, “But—drink slowly, Potter.” His eye’s bored into Harry’s, imparting the importance of following his directions to the letter.

Harry gathered his wits and nodded. Snape handed him the vial. Both wizards watched Harry intently as he pulled the stopper from the potion and raised the glass towards his mouth. As soon as the potion hit his lips, he felt a wrenching sensation in his upper jaw. And then there was pain, the tearing, ripping sort, that made Harry see black spots in his vision and cry out.

“Aaahrrrgh!” he winced, his shout turning into a strangled growl. The vial shook in his hands, and Harry put all his effort into tipping it slowly. The potion trickled down the back of his throat, soothing the fire that had risen inside of him. He drained the glass and licked his lips.

“Wha—What?” Harry exclaimed. His upper canines had elongated into what could only be described as fangs. He sucked in a surprised breath, feeling them recede into his skull as he probed them with his tongue. The sensation was unpleasant but not painful; the aches in his head and stomach had also subsided. He ran his tongue along his upper teeth again. His canines seemed to be slightly longer than they had been before, but nowhere near the size of the...fangs. He looked at Snape and Dumbledore with wide eyes.

“What’s wrong with me?” he asked again, able to keep his voice neutral and his emotions in check this time.

Snape sneered.

“You’re perfectly healthy, Potter,” he said irritably-almost as if Harry’s good health was a personal grievance to him. Harry ignored his tone and sagged against the back of the rickety chair.

“You’re just…not. Completely. Human. Anymore.” Snape finished.

“Severus!” Dumbledore admonished faintly, peering at Snape reprovingly through his half-moon spectacles. Snape stared back, unrepentant. Harry’s throat constricted.

“Well…what am I, then?” he asked in a small voice, unsure if he really wanted to hear the answer.

“What do you think, Potter?” Snape hissed venomously. “Or do you think at all?”

“That’s quite enough, Severus,” Dumbledore chided. He rounded his twinkling blue gaze on Harry.

“Unfortunately, Harry, it seems you’ve been…changed—bitten—by a vampire,” Dumbledore explained slowly, as though he could scarcely believe it himself. Harry felt his jaw go slack.

“You’re a vampire, Potter,” Snape drawled, mistaking Harry’s astonishment for confusion.

“I’m a what?” Harry questioned, hoping wildly that he’d misheard his two professors, that he hadn’t sprouted fangs when he drank that potion, and that he hadn’t tried to attack Snape at the first sign of blood.

Please let this all just be a weird dream, Harry wished.

“A vampire, Potter,” Snape repeated dryly.

“But…wouldn’t—wouldn’t I remember that? Being bitten, I mean? How could someone bite me without me knowing?” Harry worried. Snape made eye contact with him again. Harry thought he could feel a slight pressure in his head—but maybe he was imagining it. Either way, he looked away as quickly as he could without seeming scared.

“His memory hasn’t been tampered with, Headmaster,” Snape commented. Harry’s face scrunched in confusion.

Did Snape just read my mind?

Dumbledore responded before Harry could continue his train of thought.

“Do you think, Severus, that the vampire could have been in bat form?” Dumbledore queried.

Snape frowned in thought for a moment, then gave a decisive nod.

“Were you bitten by a bat anytime recently, Potter? In, shall we say, the last hour or so?” he sneered.

Harry blinked. There had been that moment during the run-in with the Whomping Willow when Scabbers had landed on his hand. He looked down at his thumb in his lap. Yes…those could be bite marks…

“Actually, I might’ve been,” Harry began without preamble, “when Ron and I ran into the Whomping Willow—Ron’s bat Scabbers—he might’ve nipped me.” He held up his thumb for the professors to see. Snape peered at it, then got up from behind his desk and Summoned a few jars and some plasters. Wordlessly, he grabbed Harry’s forearm and pulled it towards the desk. Harry resisted the urge to flinch. He didn’t want to seem squeamish or squirrely in front of either of the men. Snape waved his wand over the incisions in Harry’s thumb, and they flashed red.

“Aaah!” Harry hissed in spite of himself. It had felt like the blood in his hand was boiling.

“Well, Severus?” Dumbledore prompted mildly.

“Most definitely a vampire bite,” Snape said curtly, opening the jars and dipping his thumb and forefinger of one hand into the salve inside, “but we knew as much, owing to the appearance of the boy’s fangs.”

Dumbledore looked like he wanted to say something, but only sent a tired look Snape’s way.

“Lucky it was your thumb and not your wrist, Potter,” Snape snarled as he rubbed the salve into Harry’s wound. His words were harsh, but his touch was surprisingly gentle. “If you’d been bitten in the wrist, you could’ve bled to death or killed another student by now—would’ve drained a child of blood, completely. The venom took longer to circulate through your body because it spread through your bloodstream from the smaller blood vessels in your thumb as opposed to the larger ones in your wrist. Thus, the effects came on gradually.”

Bled to death or killed another student? Harry paled as he realized how grim the consequences were. He’d almost attacked Snape before. He had fangs. He was a vampire now. He was a bloody vampire! His brow furrowed in concentration.

“But…Scabbers is the bat that bit me. D’you mean Scabbers is a—a vampire?” Harry asked the adults, his face wrinkling in revulsion. Dumbledore nodded gravely.

“It would certainly seem so,” he said. Snape finished bandaging Harry’s hand and pinched the bridge of his nose.

“Scabbers is Ron’s familiar! And he was Percy’s before that! Don’t you think they would’ve noticed if he wasn’t a normal bat?” Harry exclaimed in disbelief.

“Vampires can survive off animal blood as well…or potions like the one I gave you,” Snape said. “Headmaster, I think it would be wise to send for all the Weasleys.” He sat back down behind his desk with an air of resignation.

“Right you are, Severus,” Dumbledore declared, brandishing his wand. “The sooner we get to the bottom of this, the better.”

With a lazy wave of his wand, an ethereal bird erupted from the tip.

“Minerva, please escort the Weasley children to Severus’s office. Do ensure that young Ronald Weasley has his bat with him,” Dumbledore spoke to the silvery bird. Silently, it flew off, leaving Harry puzzled and diverted from the matter at hand. Dumbledore jumped up.

“Severus, if I may, could I trouble you for some Veritaserum?” Dumbledore asked. Snape nodded, then jerked his head in the direction of his potions storeroom.

“Of course, Headmaster; help yourself. I’ve a few bottles already brewed and waiting in my storeroom. Do refrain from Summoning them, though—too much magic can make some potions rather—volatile,” he elaborated.

“Thank you, Severus,” Dumbledore nodded and walked off, humming tunelessly to himself. Snape remained motionless in his chair, his disconcerting stillness making Harry want to fidget. Harry was still curious about the great silver bird that had burst from the end of Dumbledore’s wand. Normally, he wouldn’t bother asking Snape a question unless he wanted a cutting and sarcastic retort for an answer. But his inquisitiveness got the better of him. Better to ponder about the pearlescent bird than dwell on his newest…problem.

“Professor,” Harry began, “what was that bird that came out of Professor Dumbledore’s wand?”

Snape raised an eyebrow, but he didn’t sneer or scoff like Harry had been expecting.

“It was a Patronus, Potter,” he replied shortly.

“What’s a—” Harry started.

“A Patronus,” Snape interrupted him, going back to pinching the bridge of his nose, “is a protector spelled into being by the caster with the emotive strength generated from a happy memory. The corporeal Patronus takes the form of an animal, but it requires considerable skill to produce. When fully formed, the Patronus can repel dementors and send messages.” Harry frowned, absorbing the information.

“What are demon—demen—” Harry huffed, trying to recall the name. Swept up in his curiosity, he’d momentarily forgotten that he and Snape were, as a rule, not on speaking terms with each other. They both preferred to keep interactions and conversations to the bare minimum—well, usually.

Snape has no problem talking to me at length when he’s telling me off, Harry thought.

“Dementors, Potter, are Dark beings that prey on human souls,” Snape’s voice dropped to a low whisper. “They are fear incarnate. Their very presence makes their victims relive their worst memories. Their most formidable and most dreaded weapon is their Kiss. They siphon the soul right out of the body, leaving behind an empty husk of a human being. The Patronus is—in essence—the opposite of the dementor.” Harry shuddered, imagining the soul-sucking Dark creatures.

“I—I can see why people would want to have Patronus guardians to fend them off, Sir,” Harry shivered. “What exactly was Professor Dumbledore’s?” He tried to keep his eagerness from showing through his voice. If Snape realized Harry was enjoying the little lecture, he’d probably put a stop to it immediately.

“The Headmaster’s Patronus is a Phoenix,” Snape said, his lip curled. “A corporeal Patronus is rare enough, but a mythical Patronus is—practically unheard of.” Harry thought he could detect hints of both jealousy and admiration in Snape’s voice. Harry knew that Snape had always fancied the Defense Against the Dark Arts position. He wondered…

“Can you produce a—what did you call it?—er, a corporeal Patronus, Sir?” Harry asked with some trepidation. Snape’s face went stony for a sliver of a second, then he gave a swift jerk of his head in the affirmative. Harry waited expectantly, looking pointedly at Snape’s wand where it was clenched in his left hand.

Snape followed his gaze and sneered, “What are you watching for, Potter? You seem to be laboring under the delusion that I intend to cast the Patronus Charm. Do you expect me to put on a little show for you? To pander to your every whim because you’re the famous Mr. Potter?”

Harry reddened with indignation, but he kept silent, training his gaze on his hands lying folded in his lap. He clenched them into fists.

I was just asking out of curiosity, I didn’t bloody well expect a show, thanks! Harry fumed to himself.

The sounds of footsteps coming from deeper within Snape’s office and outside in the corridor returned Harry’s mind to the issue at hand. He looked up from his lap to see Dumbledore approaching the desk, cradling two phials of clear liquid—the Veritaserum.

“Hi, Harry!” exclaimed two voices at the same time. Harry’s head whipped around to face the Weasleys. He beamed up at Fred and George.

“Brilliant—” said Fred.

“Inspired!” George added.

“What an entrance!”

“Flying a car right into the Whomping Willow—”

“People’ll be talking about that one for years—"

“Why couldn’t we’ve come in the car, eh?” they finished together. Harry shared an embarrassed grin with Ron, then he remembered the consequences of their escapade. He paled, and the grin was wiped off his face. Snape was scowling at the band of redheads with such fierce displeasure it seemed like he was trying to stare them out of existence—or at least out of his office.

“Ah! You’re all here,” Dumbledore observed. “Splendid! Thank you, Minerva. You've done a fine job.” Professor McGonagall dipped her head in acknowledgement of the praise.

“Now, then,” Dumbledore said, looking to Ron from behind his half-moon spectacles, “Mr. Weasley, may I be permitted to examine your familiar?”

“Scabbers?” Ron asked in confusion.

“Go on, Ron,” Percy chided, patting him on the shoulder, “Let the Headmaster take a look at Scabbers for a moment.” Fred, George, and Ginny glanced among each other in bemusement. McGonagall remained just inside the doorway, watching with mild curiosity.

Ron reached into the pocket of his robes and pulled out his bat, who seemed immensely unwilling to leave the pocket. Scabbers screeched indignantly as Ron wrestled him fully out of the pocket and handed him over to Dumbledore.

“Carpe Retractum,” Dumbledore murmured. A rope of light snaked from Dumbledore’s wand tip and coiled around the bat, fixing it in place above Dumbledore’s outstretched palm.

“Severus?” Dumbledore looked to the younger man. Snape pointed his wand at the bat and nodded.

“Just say the word, Headmaster,” he said silkily. Scabbers’s screeching grew louder as he struggled to free himself from the binding for all he was worth. His wriggling seemed only to amuse Dumbledore, who was watching the bat’s futile efforts with twinkling eyes.

“Now, Severus,” Dumbledore said. Snape brought his wand up in a jabbing motion.

“Revelio,” he hissed through bared teeth. For one terrible moment, nothing happened. Harry’s eyes left the bat and glanced around at Dumbledore, at Snape, and back at the Weasleys and McGonagall. An agonized screech snapped his attention back to the bat at once.

Scabbers was growing, changing, shifting before them. Dumbledore lengthened the rope he’d conjured to give the transformation room to pan out. Scabbers was losing his fur, his short legs were lengthening, his wings stretched into arms. His snout and ears shrank into human proportions. And suddenly, Scabbers was no more. In the bat’s place was a stubby, balding man with a pointed nose and small, watery eyes. He stood there wheezing, still struggling against the ropes, and darted his eyes to everyone in the room. There was a collective intake of breath all around.

Professor McGonagall brushed past the Weasleys in a daze.

“Peter? Peter Pettigrew? But how—” she breathed.

“Scabbers is a man!” Ron cried in horror, a hand covering his mouth. “Percy, look! Our bat is a man!” Percy gripped Ron’s and Ginny’s shoulders tightly; his mouth was opening and closing but no sound was coming out. Fred and George seemed to be engaged in silent conversation between themselves, glancing quizzically from Pettigrew to a crinkled piece of parchment one of them had gotten out.

Harry barely registered the reactions of McGonagall and the Weasleys. He was concentrated on Snape and Dumbledore, who were both rendered speechless after the transformation. Harry was stunned. He’d never seen either man so thoroughly discomfited. Dumbledore was positively gobsmacked; he was regarding Pettigrew with a mix of revulsion and amazement. For his part, Snape seemed to be far more enraged than astonished. He was too incensed to speak. A pulsing vein in his neck stood out, and his cheeks had twin splotches of angry red coloring.

And here I thought I’d seen Snape at his maddest after the flying car incident today, Harry thought grimly, but it turns out that compared to right now, he’d been positively friendly then.

“I—I let him sleep in my bed!” Ron wailed to the room at large, shaking against Percy and Ginny. This declaration seemed to snap Dumbledore and Snape back into action. Dumbledore gave himself a little shake and tightened his grip on his wand. In one fluid motion, Snape rose from his chair, strode over to his fireplace, reached into a jar on the mantel, and tossed powder onto the embers. Green flames jumped to life.

“Madam Pomfrey—Hogwarts infirmary!” he called.

“Severus?” Madam Pomfrey answered from the flames.

“I’m sending the entire Weasley brood through to you, Poppy. They’ve just witnessed something—” Snape’s lip curled as he spoke, “rather disturbing.”

Coming to her senses, McGonagall ushered the Weasleys to Snape’s fireplace and through the floo one after the other.

“Sorry, Ron,” Fred said.

“We’ll get you an owl,” George promised.