Sherlock, it turned out, was also in NEWT level Charms, Herbology, Potions, and according to the whispering students at lunch, Arithmancy and Ancient Runes. The only professors who refused his application were Binns and McGonagall, and he hadn't applied for NEWT courses in Care of Magical Creatures, Divination, or Astronomy.

John, on the other hand, had spent the day trying to figure out why the name Holmes had a familiar ring to it. He was eating treacle tart at dinner before Lindsay finally supplied the missing link.

"The Obliviator who modified my memories for the pureblood program mentioned that a Holmes had rearranged his work schedule so he could do that session."

"That's it!" John snapped his fingers. "The letter my parents received in June – it was from the office of a Holmes. Only time I saw the name, but then I read that letter about 50 times before we came back to school."

"So, this kid's father?" Lindsay speculated.

"I suppose I could ask him this evening," John said. "We're meeting in the library after this to begin that lethifold assignment for Smith. How about you and your partner?"

"We're taking different aspects of the lethifold to research and will meet up tomorrow sometime for a progress report. She seems fairly excited about the project – nice thing about having a Hufflepuff for a partner."

"Lucky. I've got the child genius who couldn't even be bothered to say that he'd agreed to be my partner," John groaned, pushing the plate back and rising from the bench. "If he brings my grade down because he's too brilliant to do the work, I'll hex him so he won't remember where the Defense Against the Dark Arts classroom is."

"No, you won't," Lindsay replied matter-of-factly.

They made their way out of the Great Hall and into the entrance. John glanced down the corridor toward the library with a heavy sigh.

"Don't suppose you have any particular need to go to the library?" he asked, half-joking.

"All my books are upstairs, and I want to get a head start on that Transfiguration assignment. But hey, if you get back soon enough we can practice those spells together."

John groaned. "All I want to do is get to bed and try and let my brain recuperate from this day. But yes, I'll probably look for you when I get back."

Lindsay grimaced her understanding and turned toward the stairs. John waved a hand and walked on toward the library. Even though it was nearly empty, it took him a while to find Sherlock, at one of the back study tables, so deeply engrossed in a book that John had to risk Madam Pince's wrath just to get his attention.

"Oh, yes, John Watson," Sherlock said, closing the book suddenly. "Lethifolds."

John sat across from him, cursing himself for feeling like he was the one who was awaiting instruction. "I was thinking we could both take half of the research. Maybe get an outline together tonight so we know what we're both doing. We don't know yet how this Smith fellow marks his assignments yet, but I'd imagine better safe than sorry."

"More on the level of Binns than McGonagall," Sherlock said with a dismissive shrug. "He'll give out E's for P level work just because he's trying this heavy-handed experiment to make everyone believe that working together somehow makes us all safer at night."

A memory of Lavender Brown as he had found her body – alone and bloody in the corner of the courtyard – sprang into John's mind. "Not a bad lesson to teach," he said stiffly. "You wouldn't know much about that, I expect."

Sherlock cocked his head at him, half-smiling. "When we met this afternoon, I asked 'courtyard or castle', and you seemed surprised."

"Well, a bit, but not now," John clarified. "You probably saw me last year or read my name in the Prophet over the summer or someone said something to you. However it happened, you're not some sort of seer whose clairvoyance will keep him protected always."

"Agreed," Sherlock said, leaning forward on the table. "But seeing things can go a long way toward keeping me safe. For example, I know you're a Muggleborn, with a sibling, probably younger, who is not magical. I know you fought in the battle of Hogwarts in May and were probably one of the instigators of the little rebellions going on last year. You were injured, but your limp is at least partly psychosomatic. You also don't trust Professor Smith or, incidentally, me."

"How?" John wished he hadn't let the word out.

"Muggleborn – when you came up to me today, you shook my hand right off. That's distinctly a Muggle greeting. Wizarding families do, naturally, but we're old-fashioned. We like the bow, the curtsy, the doffed hat – then the handshake. You didn't even start with a nod, just straight off stuck out a hand. When you did, I saw your tan line – slight browning on the hand, none past the base of your thumb. Muggle clothes doesn't have sleeves that come down that far, and the sunstreaks in your hair tell me you're in sunlight as much as you can be. So, wearing a long-sleeved garment most of the summer and not brown enough to have been on holiday with wizard friends. St. Mungo's, obviously, given the cane and the way you hold your shoulder. And speaking of the cane – your limp is very pronounced when you walk, particularly when you're unsure, as when you were walking up to me in the classroom earlier today – but you stood talking to me for several minutes without leaning on it more than a few moments, which means the root is psychosomatic."

He gestured to John's book bag on the table. "There's a quill sticking out of your bag, obviously one that you use frequently. It's not the sort you would buy at Scrivenshaft's, it's the kind that Muggles sell in bookstores for calligraphers. Not as high a quality as something you could get for a few Sickles in Diagon Alley – but you use it daily. A gift, then, from someone close to you. Family. Parents would have given you something nicer, even if it was Muggle-made. Someone who doesn't have a large cash flow yet. Sibling. Could be a friend, I grant you, but brother or sister is more likely, since you don't seem the type to have told your Muggle friends about your powers. Based on the nib metal, I'd say younger sister."

"As to the distrust: well, your face betrays you. Human beings have a finite number of facial expressions and certain among them are universal. When I see a man with eyes as narrow as yours and chin tilted up and to the side, I can only assume he expects to be lied to. I saw it when you were listening to Professor Smith, and you're making it right now – though not so strongly as before," he added, seeming interested.

"And the rebellion last year?" John heard himself ask, still about three links back in the chain of reasoning, but finding each one rang true.

"Ah, technically more of a guess, I admit, but a solid one. You are a Muggleborn who was at the battle. There were precious few of those to begin with, and even fewer who saw much action. You saw enough to get fairly seriously injured, but didn't get yourself killed in a battle of fully-qualified wizards and all manner of monsters. For you to have done both means you were ready and waiting for it. The group calling themselves Dumbledore's Army reformed last year and made no secret of the fact they were preparing to make a go of it whether Harry Potter ever came back or not. And I saw on the train that your method of breaking up a fight is to end it yourself. Obviously not afraid of a fight."

He leaned back and spread his hands. "Did I get anything wrong?"

John blinked. "No wonder you didn't bother with Divination," he said at last. "That was amazing."

"All of it? Well, that's a surprise. There's usually something," Sherlock said, smirk slipping into a real smile.

"The quill is from my aunt," John said. "She gave it to me while I was in St. Mungo's."

"Aunt! Of course, less knowledge than a sibling, just picked based on look," Sherlock muttered. "See? Always something."

"Well," John was slowly regaining his equilibrium. "You did leave out my rank in Dumbledore's Army, but I suppose I can forgive that."

Sherlock leaned back and studied him. "Second or third in command, I'd say. Not the leader. You have the presence and authority, but you waited until I'd confirmed I would be your partner before you acted. Not general, at least not yet."

John was still scrambling for words when a scream from the hallway stopped the words in his throat. Sherlock leapt to his feet and was halfway out of the library before John could grab his cane. They raced along the stacks of books, skidded past a confused Madame Pince, who was peering into the corridor, and ignored her remonstrances as they pounded through the entrance hall to the corridor that led to the kitchens and the Hufflepuff dormitory. The chestnut-haired girl John had seen with Lindsay was standing, hand over her mouth, staring at the floor. John and Sherlock halted, and John's cane skidded on the floor as he came to full stop. He realized with a lurch that he had placed it in a pool of blood.

It was a grisly sight, even for him, and he'd held Michael Corner's head as he gasped his last from an Entrail-Expelling Curse. A house elf lay mangled on the floor, torso nearly missing. A few tendons and scraps of skin stretched over the space that should have been a tiny body. The neck had been snapped, and there were claw marks on the skull and shoulder.

The girl half-collapsed against John, who let her bury her head on his shoulder. He wanted to look away, too, but the sight drew him like a magnet. Sherlock had lowered himself so he was almost prostrate on the ground and was examining the claw marks mere centimeters from the dead elf's staring, tennis ball-sized eyes. He flicked his wand and a vial appeared by his side. His wand prodded the torn edges of flesh and deposited a sample of bloody fluid from the spot where the neck savagely ended. Something caught his attention at the wound, and he bent even closer, a feverish light in his eyes. He whirled around and faced the girl.

"You. Did you see anything?" he asked, bounding to his feet in a vampirically swift motion. "An animal? Person? Shadow? Anything? Answer me!"

"Sherlock!" John snapped as the girl trembled against him. "Give her a moment. This is a shock."

"It's not as if she knew it," Sherlock countered dismissively. "It's not a person."

"His name was Chimmy. He cleans the Hufflepuff common room on Tuesdays and Sundays and he likes to leave leftovers in this corridor as a treat for Mrs. Norris." The girl's voice was shaky, but she'd lifted her head and was staring at Sherlock with a fragile sort of dignity. "He was born here and he's technically a free el-"

"If you can recite the elf's entire life story you can answer my question," Sherlock interrupted. "Did you see anything? Anything at all?"

She'd just begun to shake her head when a cohort of staff members rounded the corner – McGonagall, Sprout, Flitwick, Vector and Smith, followed by Mr. Filch wheezing, Mrs. Norris at his heels. The cat's yowl of surprise made the girl shudder. John kept his arm firmly around her shoulders.

""Explain yourselves," McGongall spluttered, staring at the carcass and the three teenagers who stood clustered around it.

"We heard the scream," John volunteered, realizing with a start that barely more than a minute could have passed since they arrived. He glanced at Sherlock, who was slipping the vial into his robes, and continued. "It was already like this when we arrived."

"Molly!" Professor Sprout exclaimed, taking the girl from John's grasp into her own embrace. John stepped aside at once. "Are you hurt? Did you see it happen?"

"No," came the shuddering, but definite voice. "I'd decided to go see if the house elves had any leftovers I could feed my cat, but when I got here –" her hand spasmed in the direction of the corpse.

Professor Smith was acting as peculiarly as Sherlock had, bending over the body, sniffing the air around the corpse, shining what appeared to be a small torch around, though why he didn't just use the wand light was beyond John. Sherlock was edging to the side, eyeing the sides of the corridor, apparently searching for something.

"I think the children should go. Pomona, why don't you take Miss Molly to the hospital wing?" He paused and waited until she looked up. "Molly Hooper, wasn't it?"

She nodded, scrubbing at her cheeks with the handkerchief Professor Sprout had just conjured, still pale but infinitely calmer. Smith smiled and chucked her gently under the chin.

"You've been a big help. Now go on with Professor Sprout. Madame Pomfrey will give you something for the shock."

They turned to go and McGonagall was about two steps behind, shepherding the two boys away.

"Not a word of this to anyone, understand? We'll be dealing with the situation right away and no point in sending people into a panic on the first day of classes." She said the words lightly, but there was no mistaking the iron intent behind them.

The secrecy didn't set right with John, who had had quite enough of such foolishness last year. To his surprise, Sherlock nodded.

"Of course, Professor," he said, with an almost too-perfect blend of seriousness and pleasantry. "We'll just collect our things from the library and be off. I'm sure they need you back there."

No sooner had McGonagall disappeared around the corner than Sherlock burst into activity. John, who had been mentally preparing himself for the trek up to the dormitories and the probable dreams he would have to deal with, was nearly dizzy with the sudden dashes from one wall to another - now kneeling on a flagstone and shining his wand light on it, now examining the lamp holder on the right wall.

"It's guttering differently that the others," Sherlock said in answer to John's raised eyebrows. "Look," he gestured as John continued to stare. "See? Those scratches on the sconce are fresh – look at the bright edges. It came this way."

John, who had been craning to see the miniscule marks, backed away immediately, wand leaping to his hand. "The thing that did that to Chimmy?"

"Chimmy?"

"The elf, Sherlock, the elf," John snapped. "The thing that ripped it to shreds came this way?"

Sherlock nodded, eyes scanning the floor of the entrance hall. "And it's still here."

John made a noise that was meant to be "what?" but came out in a strangled tumble of sound.

"Did you hear a door close? Or a crash? Glass breaking? Or something with claws this big – " Sherlock spread his hands about 10 inches. " – going up the stairs? It hasn't left the castle."

"The thing could have killed him earlier and –"

"The blood had barely begun to congeal," Sherlock cut across him, now searching up the walls with his wand lit. "It's a good jumper and climber," he said, pointing at a spot several feet above their heads.

John squinted, but couldn't discern anything on the rough surface. But he was learning that this boy didn't take kindly to stopping to explain.

"Alright, so it's what – in the rafters?" He tightened his grip on the wand, bracing himself.

Sherlock nodded, pointing his wand at the deep shadows on the cavernous ceiling. "Lumos maxima!"

The light shot through the hall, filling it completely. John took aim at – nothing. Every detail of the ceiling was revealed. No monster crouched among the rafters or cowered in the corner.

"But –" Sherlock frowned, taking several paces in different directions and peering upward. "It has to still be here."

The sound of footsteps cut him off. Professor Smith was striding toward them, brow furrowed. Sherlock extinguished his wand just as Smith noticed them and frowned.

"Now, boys, there's nothing more to see. If you're expecting more juicy details, you're out of luck."

"We were just talking," Sherlock said with shrug. "Any idea what did it?"

"I've managed to rule out Vashta Nerada and –" he cut himself off, smiling suddenly. "No, not yet. Certainly not any of us."

John and Sherlock exchanged a look. He'd sounded so unsure as he said it.

"Well," Smith said, clapping his hands together. "Off to your dormitories, the both of you. It's almost curfew."

"But –" John began, casting a glance up at the ceiling. Sherlock shook his head and yanked on his sleeve.

"Come on, John," he urged. "Madame Pince will be closing the library and I've left all my books there."

"You realize it could attack again – could kill Professor Smith right now, don't you?" John hissed.

"Unlikely. If it wanted more, it had two fine young helpings right in front of it all this time." Sherlock shook his head. "It won't strike again tonight. Besides, if it did, that would be an interesting development."