The first days of April were cold and wet. Students tracked in mud on the marble staircase, causing Filch to take up permanent post there with a mop, and heavy grey clouds hung above the tables of the Great Hall. The gloomy weather suited Severus just fine, as it meant the next bonding activity would be held inside. This was far preferable to what had happened the previous week, when Bella had led them all down to the Black Lake to participate in something she called 'tubbing'.

Tubbing, it turned out, involved forcing a person's head underwater until they gasped for air, gulping murky lake water into their lungs. Severus had hated this activity, as he had never learnt to swim growing up. It had taken every ounce of his self-control not to panic when Evan Rosier continued to hold his head down even after he had swallowed three huge lungfuls of water.

Afterwards, Severus had suggested that they crash James Potter's birthday party as a sort of palate cleanser. Bella had found the idea delightful, and as far as Severus was concerned, the look on James Potter's face when he realised he was outnumbered was worth a thousand near-drownings at Rosier's hands.

Severus smiled to himself, remembering the way James' treehouse had imploded, taking all of his birthday gifts with it. The memory was so sweet he might have been able to use it to make a Patronus. Still smirking, he pushed open the gilded door to Dungeon Thirteen.

Immediately, a foul smell singed the hair from his nostrils, and he gagged, covering his mouth. Dungeon Thirteen's normally immaculate furnishings were covered with the remains of animals. Carcasses of creatures twisted in unnatural positions were draped across the high-backed armchairs, and the white rug was stained with what he suspected was a mixture of blood, pelts, and dung. The overall effect was grotesque, and the stench was nearly unbearable.

"Severus!" Bella bounded towards him and clapped him on the shoulder. She was positively beaming, seemingly unaffected by the macabre scene. "Today's ritual will go much better for you than last week's, I think."

Severus cast a sceptical, watering eye over the animal remains littering the room. "I'd be interested to learn what part of my personality suggests I'd be delighted to find myself surrounded by dead animals."

Bella laughed and beckoned the other Intents closer. Most of them, like Severus, were finding it difficult to hide their disgust. "Don't worry about the smell, my loves! Today, we are going to learn something supremely interesting. We are going to make Inferi!"

Disgusting, but at least it's not tubbing. Severus crossed his arms. Beside him, Rabastan Lestrange looked horrified, but the other Intents merely seemed confused.

Bella let out a loud sigh. "Who here knows what Inferi are?"

"They're zombies," burst Lestrange. "Reanimated corpses that —"

Severus noticed Bella's frown and stepped in. "Not zombies, Rabastan," he said. "Zombies contain a fragment of the soul of the wizard who animates them. Inferi are more like puppets, enchanted to do their master's bidding. They lack a will of their own."

Bella's pout became a pleased smile. "Beautiful definition. Today you will learn how to create an Inferius. Human remains are in short supply — the Dark Lord needs those, you know — so we shall use animals. But don't worry," she added, as though she anticipated an outcry over the lack of human corpses. "The process is the same for both."

She divided them into pairs, placing Severus with Lestrange, whose face had turned a distinctly jaundiced shade of green.

"My great-uncle was eaten by a zombie," he explained to Severus, wincing as Bella handed them each an animal to work on. "It doesn't sit right with me, messing with the dead. I think we ought to just leave them be."

Obviously, Severus agreed, but squeamishness would not earn him a spot among the Dark Lord's inner circle. "These are just dead rodents," he said, examining the needle-like teeth in his ferret's jaw. "Even reanimated, they're hardly dangerous."

"Only if you lack imagination," said Bella. "You will be imbuing these animals with your will. They will do exactly what you want, so don't be afraid to think big."

Lestrange shuddered.

Animating the Inferi ended up being more difficult than Severus had anticipated. The process required maintaining several different spells at once, and as the finishing step, they had to use their own blood to draw runes on the carcasses.

"Make sure your runes correspond with what you want your Inferi to be able to do," instructed Bella as she watched their progress. "The more specific you can be, the better."

After about an hour, the room was full of animals shambling about with varying degrees of realism. Lestrange's rat lay curled up at his feet, the rune for 'sleep' written in blood on its pale fur.

"I hate this." Lestrange didn't bother to hide his revulsion as he stared at the rat.

Severus shrugged. His ferret was tripping over its own paws in an effort to chase its tail. "I was expecting worse."

"Show of hands, who knows how to get rid of an Inferi?" asked Bella, raising her own hand into the air.

Lestranges' hand shot up. "Fire."

"Precisely!" said Bella. "Any sort of light or heat will repel an Inferius, but fire works best. Rodolphus, would you like to demonstrate?"

Lestrange looked like he would rather eat his own socks, but he nodded. He drew a deep breath through his nose and pointed his wand at his rat, which vanished in a roaring column of flame. After the fire had burnt itself out, he lowered his wand, sagging a little.

They burned what was left of the Inferi, and then Bella made them clean the entire dungeon using rags and toothbrushes. It was nearly midnight by the time they finished, and Severus' knees hurt from scrubbing dung out of the rug.

"That's enough for tonight," Bella said at last, surveying the room. Even after a good cleaning, stains still lingered on the chairs, and the rug looked decidedly grimy. "I'll have the house-elves do the rest. Rodolphus, let's go to the kitchens for a Butterbeer — you pushed yourself tonight, and that makes me proud."

She slipped her arm around Lestranges' shoulders, the same way she had with Severus after learning the Unforgivable Curses. She leaned into him, lowering her voice, but Severus followed Mulciber and Avery out of Dungeon Thirteen before he could hear what she said.

Mulciber elbowed Severus in the side. "Guess what?"

"You need help in Charms again?"

"Very funny," deadpanned Mulciber. "But no. Look what I nicked."

He pulled his cloak aside to reveal a dead kitten tucked into a pocket of his robes. It looked almost peaceful; with its eyes closed, it could be sleeping.

"A while back, we used your de-boning spell on a cat." Mulciber's cruel smile didn't reach his icy blue eyes. "A muddy cat owned by a muddy girl. I thought she might like us to give her a new one, now that we know how."

"You're sick!" cried Avery, but he looked elated.

Severus' heart sank. That cat had belonged to Lily's friends in Gryffindor, and it sounded like Mulciber wanted to target Mary Macdonald, in particular. If it somehow got out that the Intents knew how to create Inferi — if Lily linked it back to him…

"What do you say?" Mulciber leered at Severus. "Are you in?"

Severus pressed his lips together. He had told Lily that he was trying to stay neutral, but allowing Mulciber to terrorise Lily's friends was hardly neutral behaviour. She might not forgive him so quickly for that.

Then again, she had sided with James Potter and his mates at their party, hadn't she? She hadn't so much as looked at him during the ambush in the Forbidden Forest. Not to mention she was protecting a potential werewolf, of all things. She couldn't lecture him about consorting with Dark creatures.

Severus nodded slowly, his eyes on the kitten. "I'm in."

After dinner on Tuesday, Lily walked back to Gryffindor tower with Parvana and Marlene, who was bemoaning the fact that Lily wouldn't give her the Detachable Cribbing Cuffs she'd confiscated from Eustace Fawley during Herbology.

"I'm just saying, you haven't turned them in to McGonagall yet, nobody'd be the wiser —"

"I can't risk it, Marly." Lily skipped a trick step on the stairs. "McGonagall's already got her eye on me thanks to Potter's party fiasco. I need to fly under the radar for a while."

"'Radar: a system for detecting the presence of aircraft,'" recited Marlene. "Developed by the Muggle military during the Global Wizarding War. Certain to come up on our O.W.L."

Parvana giggled. "If anyone needs the Cuffs, it's me. You've never gotten less than an Acceptable in your life."

"I'm not trying to cheat," said Marlene as they reached the fifth floor landing. "I just want to pass notes with Mary. Which would be possible if a certain red-haired someone would conveniently let those Cuffs fall out of her pocket…"

"Maybe I'll start wearing them as a fashion accessory," said Lily, grinning at Marlene's mock outrage. "Show off my power as a prefect. Make everyone jealous —"

A sudden shriek echoed from the top of the staircase. Lily stopped in her tracks, and Marlene collided with her back. "Did you hear that?"

"Yeah," said Marlene. "That sounded like —"

A second scream reached their ears. Immediately, Lily began to sprint up the staircase, with Marlene and Parvana close behind. For better or worse, five years as Gryffindors had trained them to run towards danger, rather than away from it.

On the sixth floor, they raced down the corridor and rounded the corner to see the door to the Arithmancy classroom hanging ajar. Lily yanked the door open and drew her wand as she burst into the room.

Inside, Mulciber was looming over a terrified Mary Macdonald. He was clutching something in his hands that Lily couldn't see. Mary sobbed, shaking her head as she tried to ward off whatever Mulciber was holding.

"Mary!" cried Marlene. She leapt forward, trying to separate them, but Mulciber already had his wand out. Marlene's arms snapped to her sides, and she fell to the ground, stiff as a board.

"STOP IT!" yelled Lily, pointing her wand at Mulciber. "What is WRONG with you?" Behind her, Parvana murmured a Disarming Charm, and Mulciber's wand flew out of his grasp. Mulciber merely chuckled, clomping towards them, and Lily's breath caught as she saw what he was holding.

It was a kitten with the same tabby colouring as Fletcher, but something was horribly wrong with it. Its fur was matted with blood, and its eyes were a milky white. It stretched its paws towards her, claws extended, struggling to free itself from Mulciber's grasp.

Mulciber stroked the kitten with one of his meaty hands. "I heard Mary was missing a cat. I thought she might like to have a replacement."

"That's not a cat!" wailed Mary. "It's — it attacked me — Lily, it's dead!"

The kitten's tongue lolled out of its mouth, and a wave of nausea washed over Lily as she stared at it.

Mulciber grinned at her horrified expression. "Isn't it precious? And it loves Mary, muddy blood and all."

He tossed the kitten carelessly into the air, and it landed on the floor with a sickening splat. For a moment, it didn't move, and Lily hoped it was well and truly dead. Then its limbs begin to twitch, and it staggered to its feet, making a tottering beeline towards Mary. Mary shrieked and clambered onto a desk, drawing her legs to her chest, but the kitten leapt farther than it should have been able to and sank its claws into her calf.

Mary screamed, shaking her leg frantically to dislodge the kitten, but it held fast. Rivulets of blood trickled down her leg. Lily took a deep breath and ran towards the kitten, trying to grab it, but it sank its teeth into her hand and she pulled back, swearing.

"Call it off!" she demanded, whirling towards Mulciber. "It's hurting her!"

"Oh, is it?" asked Mulciber, putting his hands behind his head. "I hadn't noticed." He made for the door, whistling, but Parvana blocked his way, pointing Mulciber's own wand at him.

"Try me," said Parvana in a low voice.

Mulciber raised an eyebrow. "Challenge accepted."

Before Lily could react, he grabbed Parvana by the wrist and twisted. There was a sickening crack, and Parvana cried out in pain. Moving quickly now, Mulciber plucked the wand from her hand and pushed her roughly to the ground. He stepped over her on his way out the door.

Rage burned through Lily's veins, and she pointed her wand at his back. "IMPEDIMENTA!"

But it was too late; the jinx ricocheted uselessly off the door frame as Mulciber ducked around the corner.

Mary shrieked again. "Lily, HELP ME!"

Lily whirled around. The kitten was crawling up Mary's leg, its claws tearing into her skin. "Petrificus Totalus!" she shouted. The spell hit the kitten on its hindquarters, sinking into its matted fur, but it continued to climb, seemingly unaffected.

"What the — why didn't that work?" cried Lily, but Mary was sobbing too hard to respond. "Diffindo!" The spell slashed three large gashes across the kitten's back but didn't slow it down. It had reached Mary's stomach and was clawing its way up her blouse, teeth bared.

"Please," whimpered Mary, trying to push the kitten away. "Stop it — please..."

"I don't know how!" exclaimed Lily, trying to pry it off Mary's shirt. "It won't — nothing works —"

There was a whooshing sound, and a jet of light hit Marlene's stiff, prone body. Lily turned to see Parvana slumped against the wall, one hand cradled in her lap and the other pointing her wand at Marlene.

Marlene bolted upright as soon as the countercurse hit her. "I am going to murder Mulciber," she growled. "Thanks for that, Parvana. You alright?"

"I'm fine." Parvana's breathing was shallow. "Help Mary. Please."

"Right." Marlene turned around. "Lily, this disgusting thing is undead."

"Yeah, I can see that myself, actually." Lily sent another ineffective Cutting Hex at the kitten, which had nearly reached Mary's neck.

"Fire," said Parvana slowly, her eyes widening. "We need to use fire."

"Exactly." Marlene's expression was grim. "Mary, cover your face, I don't want you getting burned. Lily, Parvana, Incendios on three." Slightly perplexed, Lily nodded, holding her wand out. "One… two… three!"

Three Fire-Making Spells streaked towards the kitten like missiles, setting it ablaze. It tumbled to the floor, writhing, something akin to a scream coming from its mouth. The pillar of fire flared brightly, and the kitten was consumed. The flames burnt out as if nothing had ever happened — there wasn't even a trace of ashes where the kitten had been.

Marlene held Mary as she sobbed. "Shh, it's alright," she cooed, stroking Mary's hair. "It's gone now. It can't hurt you anymore."

Lily knelt beside Mary to examine her legs. The scratches were long and deep, and they continued to bleed. "We have to get you to Madam Pomfrey."

Mary shook her head, hiccuping. "I can't walk to the hospital wing like this. If someone sees… I don't want the whole school to know…"

"You stay here then, and I'll go get her," said Lily determinedly.

"I'll come, too." Parvana straightened shakily. "Better to go in twos. Plus…" She gestured to her wrist, which was bent at an odd angle.

"Are you going to tell Pomfrey what happened?" asked Lily as they stepped into the corridor.

"That I had Mulciber wandless and he still managed to get the better of me?" said Parvana, giving Lily a wan smile. "No, thanks. I'd rather her think it was a Quidditch accident."

Lily frowned. "We can't let him get away with this."

"Yeah, but what can Madam Pomfrey do?" asked Parvana. "Besides, it's just a broken wrist. I mean, it definitely hurts, but it takes about a minute to fix."

Lily raised her eyebrows. "You know, in the Muggle world, breaking a bone is kind of a big deal."

"Is it?"

"Yeah. You have to wear a plaster cast — sort of like a brace — for months, and you can't get it wet. It's annoying and itchy, and takes a long time to heal."

"Makes me glad I'm a witch," said Parvana, wincing as she examined her wrist. "I'll just have to get him back the next time we play Slytherin in Quidditch."

When they got to the hospital wing, Madam Pomfrey noticed Parvana's injury immediately and indeed was able to mend it in less than two minutes. As the Mediwitch gently flexed Parvana's newly-healed wrist, Parvana caught Lily's gobsmacked expression and smiled a little. "Quicker than a plaster cast?"

"You have no idea," said Lily. "Also, Madam Pomfrey, we were hoping… there's someone else, upstairs, who you should see…"

Madam Pomfrey took one look at the seriousness of their faces and followed them back to the Arithmancy classroom. Marlene was still holding Mary, who had stopped crying and was now staring blankly into the distance, a dazed expression on her face.

Madam Pomfrey clucked her tongue as she examined the oozing cuts on Mary's leg. "These were caused by Dark magic, were they not?"

"Yeah," said Marlene hoarsely.

Madam Pomfrey shook her head and pulled a jar full of a foul-smelling poultice out of her robes. She dipped a finger inside and dabbed Mary's wounds with it, staunching the bleeding. "What happened?"

"Dunno," said Mary dully.

Madam Pomfrey's head snapped up and she fixed Mary with a stern look. "Young lady. You have nothing to gain by protecting whoever did this to you." She turned her steely gaze to Parvana, who swallowed nervously. "And I'm supposed to believe you broke your wrist in a Quidditch accident?"

"It wasn't a person," said Mary. "It was a creature. And we — well, they — dealt with it."

Marlene looked at Mary in alarm, but Mary kept her eyes fixed on the poultice Madam Pomfrey was slathering on her legs.

"A creature," repeated Madam Pomfrey, shaking her head. "Well, then. I can't force you to tell me the details. But I think it would do some good if you were to speak with a qualified adult about this situation."

With that, she pulled out her wand and began to murmur an incantation that sounded more like a song. Lily watched in amazement as the gashes on Mary's legs knit back together, leaving only thin, pale scars.

"What sort of spell was that?" asked Lily once Madam Pomfrey had finished. "It didn't sound like anything I've ever heard before."

"It manipulates the layers of the skin," replied Madam Pomfrey, stowing her wand in her robes. "Heals superficial cuts easily enough, though it takes some finesse to leave a clean finish. Dark magic has a tendency to scar, but these should fade in a week or so." She turned towards Mary once again. "Please, Miss Macdonald — is there anything else you would like to tell me about what happened this evening?"

"No, ma'am," said Mary softly. "Thank you, though."

Madam Pomfrey clucked her tongue, muttered something that sounded like 'children', and bustled out of the room.

After she had gone, Lily, Marlene, and Parvana helped Mary back to the Gryffindor dormitory and tucked her into bed. Lily handed Mary a vial of Dreamless Sleep, which Madam Pomfrey had instructed she take to prevent the formation of anxieties related to the attack. Mary downed the vial without complaint, then closed her eyes. Her chest rose and fell as her breathing slowed.

"One thing is still bothering me," said Lily once she was certain that Mary was asleep. "How did you know to use fire?"

Marlene shrugged. "Everybody knows that, don't they? There are all those children's stories about zombies, Inferi, and the like, and the hero always uses some kind of fire spell to get rid of them."

"In Muggle stories, you have to kill a zombie by taking out its brains," Lily said. "That's what I was trying to do. I thought… if I could get to its skull…"

Marlene shook her head. "Nah. It doesn't work like that."

Parvana smiled a little. "First broken bones, now zombies. Muggles have some odd ideas, don't they?"

"That's one way of putting it," muttered Lily. This was the third time in recent weeks that she'd been caught out for lacking what was apparently common knowledge in the wizarding world. She wondered if this pattern would continue throughout her life — maybe when she was a crotchety old witch, her neighbours would laugh at her for being so ignorant. And what was she missing from the Muggle world, by being so immersed in the wizarding one?

Marlene was watching Mary sleep soundly. "I worry about her," Marlene murmured into Lily's ear. "And about you, too."

Lily looked at her, surprised. "I'm not the one Mulciber attacked with a zombie kitten."

"No, but you're a Muggle-born like she is," said Marlene. "It feels like the war is getting closer, and it makes me nervous."

Lily knew what Marlene meant. During her previous years at Hogwarts, it hadn't been so important that her parents were Muggles, but now it seemed like she was constantly being reminded that she was an outsider. "Just because Mulciber has a case of pure-blood fever doesn't mean we're at war,"

"Not yet, at least," said Marlene.

Lily sighed and rested her head on Marlene's shoulder. "Not yet."

Severus spent the next week doing his best to track the movements of Remus Lupin and his friends, especially after dinner, when he figured they were most likely to sneak out. The full moon was only days away, and he hoped they'd let something slip when they didn't realise he was listening.

Unfortunately, he hadn't overheard anything enlightening so far. All four Gryffindor boys were still being punished for being stupid enough to throw a party in the Forbidden Forest, so after dinner they usually split up to serve their separate detentions. James would head to the kitchens, where Severus assumed he was tasked with helping the house-elves tidy up. Peter went to the dungeons to sort through Slughorn's potions cabinet, and Sirius and Remus would vanish up Hogwarts' many flights of stairs, presumably doing something tedious for McGonagall or Flitwick.

Severus got his chance the night of the full moon. Remus Lupin wasn't at dinner, and Sirius lingered at the Gryffindor table long after James and Peter had gone to their detentions. Finally, Sirius slipped out of the Great Hall alone. After waiting a minute, Severus followed him into the Entrance Hall, where he was just in time to see Sirius bounding up the marble staircase and out of sight.

Severus slung his bag over his shoulder and followed as quickly as he could, trying not to draw attention to himself. He reached the first floor landing just in time to see Sirius vanish around a corner.

Severus' heart pounded, both from excitement and the exertion of using his scrawny legs to sprint up the stairs. Sirius was going to the hospital wing. This was new.

The infirmary corridor was empty by the time Severus reached it. He crept forward and pressed his ear to the door, but no noise came from inside. He took a deep breath and quietly pushed the door open.

As soon as he stepped inside, a pair of hands grabbed him by the collar and shoved him roughly onto a nearby cot.

"I knew it," said Sirius triumphantly, drawing the curtains around the cot. "You are following us. I told James, but he didn't believe me."

Severus tried to pull out his wand, but Sirius was ready for it. He grabbed a handful of Severus' hair and shoved him onto the cot, snatching the wand from his hands.

"Stop — give that back," said Severus, scrambling into a sitting position.

Sirius quirked an eyebrow, twirling the wand between his fingers. "Or else you'll what? Punch me? I'd like to see you try."

"You think you're hot stuff, don't you?" sneered Severus. "Firstborn of the House of Black, think you can shove around whoever you want —"

"Not whoever I want, Snivellus," said Sirius, feigning a yawn. "Just you, really."

"Why did you lure me here?"

"Lure?" repeated Sirius incredulously. "I didn't lure you anywhere. I was minding my own business, and you followed me like the little sneak you are. Just like you followed us to the Shrieking Shack. And to our party."

Suddenly, Sirius lunged and grabbed Severus' arms, forcing him back onto the cot and pinning him down. Severus thrashed, trying to twist free, but it was no use. Weeks of running drills with the other Intents had given his undernourished frame an ounce of much-needed muscle, but he was no match for Sirius, who was tall and strongly built.

"I heard something interesting from Remus at that party." Sirius' breath was hot against Severus' ear. "Lily told him you've been coming up with theories about his illness."

"Not theories," snarled Severus, trying to push Sirius off of him. "Facts."

Sirius grinned, clearly enjoying watching Severus struggle. "Theories and gossip and speculation, Snivellus. Unless you've seen him transform with your own two eyes?"

"So you admit he transforms?"

Sirius let go of him then, but before Severus could sit up, Sirius grabbed him by the front of his robes and hauled him against the wall, his wand pressed into Severus' throat.

"I admit nothing," growled Sirius. "But if you're so intent on finding out, why don't you follow the tunnel under the Whomping Willow and see where it leads?"

"Tell me how to get past the branches," wheezed Severus. Sirius' wand was cutting into his windpipe.

"Easy," said Sirius. "Touch the knot at the base of the Whomping Willow. Password to the tunnel's 'open sesame.'"

He released Severus, who staggered backwards, willing himself to maintain his balance.

"And when I kill the monster you call a friend?" rasped Severus, massaging his throat.

Sirius barked a laugh. "You're a joke, you know that, Snivellus? You couldn't so much as singe a single hair on his head. Or hide, as the case may be." He winked, then checked his watch, which was cheap and obviously made by Muggles. He probably thought it made him look cool. "Pomfrey's already left with Remus, so I'd say you've got, what, half an hour till moonrise? Make sure to cast that Disillusionment charm you do so well, so she doesn't see you on her way back to the castle."

He held Severus' wand out. Severus took it, eyeing Sirius sceptically. "Why are you telling me all this?"

"It's quite straightforward, really," said Sirius airily. "If you want to know what's wrong with Remus so badly, you deserve to find out." He pulled back the curtains to expose the empty hospital wing before turning back to Severus, a mad light dancing in his eyes. "When you see him, give Remus my regards."

James collapsed into a squashy armchair in the Gryffindor common room, rubbing his hands. The skin around his nails was dry and cracked from washing dishes with the house-elves in the kitchens. He actually found his detentions quite pleasant, so far — he enjoyed the mindless rhythm of scrubbing the pots and pans until they were sparkling clean, and the house-elves always gave him sweets at the end of the night.

Peter passed him a jar of snail essence. "Sirius still in detention?"

"Guess so." James twisted the lid off the jar and scooped out a handful of greyish slime. "Fancy a game of Exploding Snap?"

They had played three rounds of Exploding Snap and were halfway through building an elaborate card castle when Sirius crawled through the portrait hole, grinning.

"Exploding Snap?" asked Sirius, joining them at the table. "I've got a better game for you. It's called… wait for it… Exploding Snape."

Peter groaned, but James laughed, stacking another card atop the castle. "I'm in. How do we play? Slipping as many firecrackers as possible into Snape's dirty old bag?"

"Better," said Sirius, grinning. "First, we watch as Snivellus sneaks down to the Whomping Willow. Then we laugh at the look on his face when he realises he's about to be mauled by a werewolf, and it's his own damn fault."

It was Peter's turn to laugh this time, but James frowned. "What do you mean?"

"I mean he was snooping around like usual, wanting to know what's wrong with Remus, so I told him to go find out," said Sirius with a shrug.

Peter sniggered. "I'd like to see him try to get past the Whomping Willow."

"Oh, I told him how," said Sirius, waving his hand. "Not that it wouldn't be amusing watching him try to avoid its branches, but I figured it was best to cut to the chase."

"Sirius," said James slowly, "please tell me you're joking."

"Of course I'm not joking," said Sirius. "The nosy git wants to go toe-to-toe with a bloody werewolf. Who am I to withhold information in the presence of such stupidity?"

"Sirius, that's not a werewolf, it's Remus," said James, jumping to his feet. The movement knocked over the card castle, which exploded with a noise like a gunshot, dusting their robes with soot.

"Is it really Remus, though?" said Peter thoughtfully. "I've always been unclear if Remus and the wolf are one and the same, like with Animagi, or if he disappears entirely when he transforms, leaving behind only the wolf… not many texts on the philosophy of lycanthropy in the library, you know…"

"Regardless, Pete, they're not gonna put the wolf on trial when Snape gets killed," snapped James. He strode towards the portrait hole, and Sirius made to follow him, but James whirled around, pointing his wand at Sirius' throat.

"You're not coming," said James in a low voice. "You're going to Dumbledore and telling him exactly what you did. Then you lot are going to pray that I get to Snape before Remus does."

He barely registered the look of shock on Sirius' face before he was off, scrambling out the portrait hole and through the castle as quickly as he could. He sprinted onto the grounds, ignoring the wind that whipped around him, chilling him to the bone.

When he reached the Whomping Willow, he darted towards the base of the tree, not bothering to freeze its branches. One particularly large bough came crashing towards him, and he flung himself onto his stomach, rolling out of the way. Many smaller branches lashed at him like whips; one struck him across the shoulder and he swore, crawling to the tunnel which lay at the base of the tree.

He flung himself into the tunnel headfirst, nearly knocking his chin against a root that jutted up from the ground.

"SNAPE!" bellowed James, but there was no response. He ran through the tunnel as quickly as he could, bent nearly in two and scrabbling with his arms to find purchase against the uneven ground.

Finally, a faint light gleamed at the end of the tunnel, coming from the trapdoor that led to the Shrieking Shack. James drew his wand, and his stomach turned as he realised that Severus wasn't there. He leapt upwards and reached for the handle on the trapdoor, ready to pull it down and face the wolf on the other side —

He collided mid-air with something solid and invisible and tumbled to the ground. It felt like he was lying atop a tangle of limbs, a body… he could see a dim outline that moved as the body fought to throw him off…

"Snape?!" exclaimed James, scrambling to his feet.

"Come to see the show?" sneered Severus, who had Disillusioned himself so well that James could barely tell he was there.

"Snape, we have to go," panted James. "It's not safe —"

"You don't say." Severus' voice dripped with sarcasm. "Thanks for the offer, but you're stupider than you look if you seriously think I'm not going to find out what's up there."

He reached a shimmery hand up, grasping the handle of the trapdoor. James tackled him, and they fell in a jumble to the ground, but not before the trapdoor above them swung open.

Light flooded the tunnel, and James looked up, squinting. He could see the drawing room of the Shrieking Shack above him, all its furniture where it should be.

Then something growled, long and low, and a dark shape blocked the entrance to the Shrieking Shack.

Instinctively, James threw his arms out, shielding Severus, even as a part of his brain told him it was crazy to do so, since Severus was Disillusioned. He, James, was the only human the wolf would see —

"Lumos!" shouted Severus, and light illuminated the tunnel. The wolf's pupils contracted to pinpoints; it had human eyes, brown and round and grotesquely familiar. It bared its fangs.

It lunged as James raised his wand. "STUPEFY!"

The spell ricocheted off the wolf's pelt, and it stumbled backwards. Its hindquarters were still in the Shack, but its front hung out the trapdoor. It snapped its slavering jaws as its claws slashed through the air, tearing at James' robes.

"STUPEFY!" cried James again, but the spell merely glanced off the wolf's muzzle. It shook its head, annoyed, and readied itself to leap into the tunnel. Frantically, James pointed his wand at the trapdoor, praying his next spell would work. "COLLOPORTUS!"

The trapdoor swung upward right as the wolf lunged. The door forced it backwards, and the wolf snarled, its paws scrabbling for purchase. At last, the door slammed shut. The wolf was trapped inside the Shrieking Shack.

James kept his wand pointed at the trapdoor, breathing heavily. An anguished, eerily human moan sounded inside the Shack, followed by a loud bang. The wolf had flung itself against the trapdoor, which shuddered under its weight.

"ARE YOU HAPPY NOW, SNAPE?" bellowed James, pushing him down the tunnel. "RUN!"

Severus didn't need telling twice. He fled, his Disillusioned outline disappearing into the darkness of the tunnel. James' heart hammered violently in his chest as he sprinted after him. More bangs came from behind them, followed by the splintering of wood. Please let the door hold, please let it hold…

The branches of the Whomping Willow were still as James hauled himself out of the tunnel. In front of him, Severus was panting, hands on his knees. Severus tapped his wand to his head, undoing his Disillusionment Charm. When he looked at James, fury burned in his black eyes.

"I didn't ask you to —"

"You're lucky I did," spat James. He was shaking, but he didn't know if it was from adrenaline or the cold or something else. "You were inches away from a werewolf, and your spell of choice is Lumos? You stupid, nosy, half-brained —"

"I think that's quite enough, Mr Potter," said a calm voice. James turned to see a tall, white-bearded figure striding towards them, followed by Sirius.

"Would you two be so kind as to accompany me to my office?" said Albus Dumbledore. It wasn't a question.