Friday, 15th June 1973

Remus' brilliant idea to "do something fun" resulted in a brainstorming session, which inevitably led to a plan to play one last joke on the unsuspecting population of Hogwarts before everyone went home for the summer, and that had brought them to the library to search for the spells they needed to pull it off. Admittedly, five hours had passed since the original idea, which was much longer than they'd thought it would take, but they were finally ready to start. And despite the looming full moon, there was plenty of time left to do it, but Peter disagreed, apparently.

'The moon rises in less than an hour. I just think it's too late. You should leave it to us and go to the Shack.'

Remus tried very hard not to get annoyed by Peter's over-protectiveness. He just didn't understand how effective his potion was. That was all. There really wasn't anything to worry about. He felt amazing. Invincible even. Nothing would go wrong. Nothing could go wrong. They were the Marauders, and the Marauders always succeeded.

'It was my idea. You're not leaving me out,' Remus told him. 'And I feel great, anyway. I could run to the Whomping Willow if I have to. Which I won't because we have plenty of time.'

'Remus knows best what he can manage,' James said, interrupting the argument. 'You're being a bit controlling, Bubbles.'

Sirius nodded. 'And we're just wasting more time by sitting here arguing about it.'

'Fine,' Peter said, holding his hands up in surrender. 'But at least give Slytherin to Remus. It's closest to the entrance.'

'That works for me,' Remus said, grinning at his triumph.

'You can do Hufflepuff, then, Bubbles,' James said. 'Twinkles can do Ravenclaw, and I'll fly around and do the windows of the Towers. We'll do Gryffindor on the way out.'

'Aye, aye, Sunshine,' Sirius said, giving him a mock salute.

Casting the spells on the entrance to Gryffindor Tower went well enough. They had to do it from under the cloak so the Fat Lady wouldn't see them, and it was awkward—Remus took an elbow to the ribs on three separate occasions—but they got it done and then they split up, Sirius breaking off from the main group at the top of the Grand Staircase to head to Ravenclaw, James leaving them at the Entrance Hall, and Remus and Peter travelling down to the subterranean level together before parting ways.

'Keep an eye on the time, yeah?' Peter said, before leaving.

Remus rolled his eyes. 'Of course. This isn't my first full moon, you know?'

'Yeah, I know. It's just…' Peter trailed off, looking at him with worried eyes. 'You seem a bit more reckless than usual.'

'I'm not being reckless. I just feel better than I normally do on a new moon. Your potion is amazing, Bubbles. You really have nothing to be worried about, I promise.'

Peter didn't sound entirely convinced when he said, 'Alright, let's get this done, then,' but Remus decided to ignore the tone of his voice and take his words at face value, tossing a wave over his shoulder as he walked away from him.

'I'll see you at the Shack in half an hour.'

It turned out to be more difficult to cast the necessary spell chain alone, not least because he kept being interrupted by Slytherins entering and leaving their common room. Luckily, his hearing was at its most sensitive and he had plenty of time to hide when he heard someone coming, so no one saw him. The interruptions cost him time, though, because each time they happened, he had to start over. The spells needed to be cast one after the other. Even a few seconds between them caused the whole thing to collapse and dissipate into the air. It was incredibly frustrating—didn't the Slytherins have anything better to do than wander the school on the last night of term?—but Remus was damned if he was going to give up and leave the Slytherins the only ones to not receive the Marauders going home gift to the school.

By the time he was finished, he only had twenty minutes left to get to the Shack, but he wasn't worried. He still felt amazing, and he was close to jogging as he speed-walked away from the scene of the crime. He hadn't moved so fast without pain for years. It was fantastic.

He was passing the door to the old Defence corridor when the smell caught his attention, and had it been any other scent, he would have ignored it and continued on his way, but, instead, he stopped dead in his tracks, inhaling deeply. There was no mistaking it. The scent was a mixture of Professor Tenebris and Regulus. Why would they be in the old Defence corridor together? He checked his watch—fifteen minutes. It was enough to go in and see what they were doing and still make it if he ran. And he felt more than capable of running.

When he pushed the door open, the scent of Regulus was stronger and it made his mouth water, which was worrying. That only happened when the person's blood was open to the air. All the doors in the corridor were shut up tight apart from one; the door to the old Defence classroom was hanging open, and the smell was coming from inside. There was no noise coming from the room, but as he moved closer, a quiet moan drifted out, making Remus' anxiety about what he was going to find inside increase tenfold. He felt terrible thinking it, but if it was what he suspected, then he needed to hurry, and if he was wrong, then Professor Tenebris never needed to know he'd thought it a possibility.

Pulling out his wand, he stepped up to the edge of the door and peered around it to get a look inside. And what he saw made his heart sink. Looking like every ugly stereotype of vampires there was, Professor Tenebris held Regulus in a vice-like grip. His body faced away from her and she had him pinned in place with one hand over his mouth and her other arm across his chest as she drank from his neck. Regulus' face was blank, but tears ran down his cheeks as he lay limp in her embrace. When Remus met his gaze, he gave no outward reaction to his presence, but hope flared to life in his eyes.

Professor Tenebris must have noticed a change in Regulus' heartbeat, or maybe she sensed Remus' presence, but something tipped her off because her eyes shot open and made direct contact with his. Lifting her face from Regulus' neck, she licked the blood from her lips before speaking.

'Don't you have somewhere to be tonight, Remus?'

'There's still time,' Remus replied, stepping around the door frame and into the room. 'You need to stop, Storm. You know you need to stop. They'll kill you for this.' He hoped that the use of the nickname the Marauders had given her would break through whatever hold the blood had over her.

She was still holding on to Regulus, and she pulled him closer to her body at Remus' words. 'I can't. You don't understand. I need it. Just go and forget you saw anything. No one will find out. How many things have I "forgotten" for you? Hm?'

'It's not the same,' Remus said softly, feeling intensely sorry for her, but he couldn't let her continue. 'We weren't hurting anyone. I can't let you do this. That's Sirius' brother.'

A smirk spread across her face and in one swift move, she pushed Regulus away from her and drew her wand. 'I'd like to see you try to stop me.'

And then they were duelling, flinging spells at each other while Regulus stood off to the side, seeming unbothered, with blood dripping down his neck and his face still blank. What had she done to him?

The room was still littered with desks and chairs, and Remus took cover behind an overturned table to catch his breath. 'Regulus!' he shouted. 'You need to get out of here.'

'He won't leave until I tell him to,' Professor Tenebris said. 'And you don't have time for this, Remus. You know what will happen if you're late for your appointment.'

'Then let Regulus go,' Remus said, pleading with her now. 'We can forget this ever happened. I won't tell anyone and you can go do those things you have to do.' Then he raised his voice to a shout. 'Regulus, you need to fight. Whatever she's done to you, you can fight it off. I know you can. It just takes willpower, and no one has more of that than you.'

She laughed, stalking towards his hiding place, but there was no humour in it. 'It doesn't matter whether you tell or not, but you are going to leave. Imperio.'

'Protego,' Remus shouted, throwing up a shield to protect him from the unknown spell, but it went straight through, hitting him in the chest and everything was suddenly fine. He didn't know what he'd been so worried about. And why was he crouching behind an overturned desk? He stood up.

'That's better. You're going to run to the Shrieking Shack now, get undressed, and lock yourself inside.'

Remus nodded. What a good idea! He would go at once. There was nothing he wanted to do more than run to the Shrieking Shack, remove his clothes, and lock himself inside. It was his entire life's purpose, and he wouldn't let anything stop him from completing it.

'Stupefy.' Regulus' voice said, his tone completely calm, and Professor Tenebris dropped to the floor like a stone. Remus didn't take any notice, turning for the door to follow the instructions he'd been given. But then Regulus' voice came again. 'Finite incantatum.'

The fog of serenity lifted, and Remus could think again. It took him a moment to take in the scene before him, Professor Tenebris laying in a crumpled heap on the floor with Regulus' wand pointed at her, and then he met Regulus' gaze. 'You did it.'

'She bit me,' he said, holding a hand to his still bleeding neck. 'She Imperiused me, and then she bit me.'

'She's a vampire.'

Staying weirdly calm considering what had happened, Regulus nodded. 'That makes sense. Do you want to guard her while I get a teacher?'

There was no pain because of the potion, but Remus was still aware of the snap as one of the bones in his leg broke, possibly because the leg gave way beneath him and he fell to the floor. 'Fuck.'

'Remus? Are you okay?'

He was out of time. Oh gods, he was out of time and still inside Hogwarts. 'No. And there's nothing you can do to help me. You have to leave, Regulus. Leave, lock the door behind you, and then get as far away as possible.'

'Why?' Regulus asked, watching as Remus moved onto all fours. 'What's happening to you?'

The quickest way to get Regulus to obey was going to be the truth, so Remus turned his face to the ground. He didn't want to see the fear and disgust that would no doubt cross his features, especially when those features were so similar to Sirius'. 'Because the full moon just rose above the horizon, and I'm a werewolf. Now get out!'

Regulus didn't respond, but Remus heard his footsteps as he hurried to the door, followed by a bang as it closed, and Regulus' voice on the other side, shaky but clear. 'Colloportus.'

Remus let out a breath. Regulus was safe, and Moony was locked in. It was far from ideal, but at least he wouldn't be able to go rampaging through the school. Then, his gaze fell on Professor Tenebris still slumped in a heap on the floor, and his relief vanished in an instant. He would kill her. Moony would take one sniff and he would rip her apart. And the only thing Remus could do to prevent it was revive her so she could leave, but Regulus was still out there. He hadn't run far away like Remus had told him to. He could hear him breathing on the other side of the door.

He couldn't sacrifice Sirius' brother for Professor Tenebris.

He was going to kill her.

That was his last thought before the pain overwhelmed the magic in the potion, and he screamed.

Sirius had finally finished layering the spells on the Entrance to Ravenclaws' common room. It had taken forever because the Ravenclaws were ridiculously active for the last night of term. What they could possibly be doing that necessitated them leaving and returning so much, he had no idea. And it was doubly annoying because it sometimes took them several minutes to figure out the answer to the riddle to gain access and get the hell out of his way.

But he was finally done. Shoving his wand into his holster, he dashed down the short staircase to the seventh floor before taking a sharp right, planning to take the slide to the ground floor so he could get to Remus quicker. The moon would be rising any minute, and he wanted to be there when Moony woke up.

He was almost at the statue of a dancing child when he heard Remus' voice in his head. I'm too late.

The words sent a bolt of ice down Sirius' spine, and he jumped into action immediately. 'Reperio.'

The rope tugged him forward, to the slide, but he went the other way instead. He needed to find a teacher on the way—maybe professor Tenebris?—even with the spell to give Remus his control back for sixty-eight seconds, they couldn't risk trying to deal with it alone if Remus hadn't made it to the Shack in time. How far had he got? Was he still in the castle or outside on the grounds? There shouldn't be anyone out there—it was well past curfew—but that didn't mean there wouldn't be.

Sirius barrelled down the Grand Staircase, heading for Professor Tenebris' quarters, hoping to the gods she would be there, and concentrated on his fear to send a message to Peter. Tell James that Remus didn't make it to the shack and come find me.

The invisible rope didn't seem to mind that he'd ignored its directions since he was still heading towards Remus, and after an initial jolt back to the slide, it adjusted, pulling him down the stairs instead. He was just passing the fifth floor when he heard a shout. 'Mister Black! Hold it right there.' It was Minnie. Thank Merlin for Minnie.

'Can't. No time,' he shouted back. 'Follow me.'

Hearing her break into a run, he slowed a little so she could catch up.

'Shouldn't you be at the Whomping Willow by now?' she asked when she fell into step next to him.

Sirius glanced at her. She was holding the front of her robes up so the hem was level with her ankles as she dashed down the stairs next to him. 'We were… doing something, and Remus didn't make it to the Shack in time. I just heard him in my head. I don't know where he is, but the tracking spell is taking me to him.'

'Fuck,' Professor McGonagall said, making Sirius' eyes widen, and she sped up.

When they reached the Entrance Hall, the rope tugged him towards the stairs that led down into the dungeons, not the door to the grounds, and Sirius' fear increased. 'He's in the dungeons.'

Professor McGonagall was breathless when she answered, causing her words to be separated by gasps for breath. 'Hopefully, he's locked himself in a room somewhere. How long do we have?'

Sirius checked his watch as they continued to run, and it took him a long moment to read the clock face with the way his arm was bouncing, but he finally worked it out. 'About three minutes.'

His admiration for his favourite teacher grew as, despite clearly struggling to keep up the pace, she didn't slow for a moment, following Sirius around corners and down corridors until they reached the door to the old Defence corridor. Skidding to a stop, Sirius reached out and tried the handle and it swung open easily.

'Regulus?' he gasped, startled to see his little brother sitting on the floor opposite the old Defence classroom with his back to the wall, hugging his knees to his chest. Then he heard Remus scream from inside the room. 'Shit.'

'He's a werewolf,' Regulus said, looking up at Sirius. His face was streaked with tears, and Sirius' heart broke as words poured from Regulus' mouth like water. 'Your friend, Remus, he's a werewolf, and Professor Tenebris is a vampire. She bit me, but Remus came to save me and then he started transforming. He told me to get out and lock the door, so I did, but Professor Tenebris is still in there. She's stunned. I stunned her.'

'How long now?' Professor McGonagall asked, striding over and looking at the door.

'Less than a minute,' Sirius said. 'I can't say exactly.'

'You already knew?' Regulus asked, but Sirius ignored him. There'd be time for that later.

'Lock the door after me,' Professor McGonagall said, pulling out her wand and pointing it at the door. 'Alohomora.'

'You can't go in there,' Sirius gasped.

'Do as you're told, Mister Black. And take your brother to Madam Pomfrey.' And with that, she pushed the door open and walked inside, slamming it closed in Sirius' face. Feeling numb, Sirius pointed his own wand at the door and twirled it clockwise. 'Colloportus.'

The tracking spell was still tugging on him, and he rested his forehead against the door, trying to ignore the sensation that was becoming more insistent with every second that passed.

That was when the door to the corridor burst open and James and Peter rushed in.

'Where is he?' James asked, pausing to survey the scene.

'In there,' Sirius said, nodding at the door. 'With Storm and Minnie. Storm's unconsciousness, Minnie went in after him. Told me to take Reggie to Pomfrey.'

'Right,' James said, taking charge. 'Let's do that then. I'm sure Minnie knows what she's doing.' He went to Regulus' side and offered him a hand, which surprisingly Regulus accepted, allowing James to pull him to his feet.

Meanwhile, Peter approached Sirius. 'You used the spell to find him, didn't you?' he asked in a low voice and when Sirius nodded. 'Do you need me to stun you?'

'No, I can fight it.' Sirius turned away from the door, determinedly ignoring the growing pain tugging at his chest, and followed the others out of the corridor.

'There's a shortcut to the entrance hall just through here,' Regulus told them, leading them to a tapestry, and sure enough, behind it was a staircase leading straight up to the Entrance Hall, coming out behind the Grand Staircase.

Briefly, the question crossed Sirius' mind as to why the tracking spell hadn't taken him down that way, but he was distracted by a sudden change in the direction he was being tugged. All the way up the stairs, the invisible rope had been trying to make him go back down, but now, it wanted him to go outside, and he broke from the group, dashing across the Entrance Hall and shoved the door open, coming to a screeching halt on the threshold.

Minerva stepped through the door and into the room where Lupin was currently undergoing his monthly transformation and slammed the door closed behind her, cutting off any further protests from Mister Black. She heard the lock click and smiled that he was following her instructions as she surveyed the room.

Lupin was on all fours. His legs and arms had fully transformed and his torso seemed close to finished, but his face was still his own and it was honestly creepy to look at. But she shook off those feelings. There wasn't time. Deasura was lying on the floor, eyes closed and blood smeared across her lips, on the other side of Remus. She would have to pass him to reach her and pass him again to take her to the door. Levitating her would take even longer, and she didn't know how much time she had. The priority had to be getting Lupin out of there. The door wouldn't hold a werewolf and she definitely didn't have time to cast all the spells to reinforce it.

'You can't be here,' Remus said, his voice sounding choked with a hint of a growl in it. 'Get out.'

'I'm not going to let you hurt anyone, Remus. That's a promise,' she told him, flicking her wand at Emhio's pool. The sound of stone scraping against stone filled the room, followed by the gush of water streaming in from the Black Lake. 'Can you move?' she asked, pulling her spare wand from its leg holster before banishing her robes to her quarters, leaving her standing in her underwear.

'Yes.'

'Then move away from Professor Tenebris, towards the pool as quick as you can manage.'

Professor McGonagall didn't wait, striding over to the pool and climbing in. She pointed her wand at herself and cast a water-breathing spell before aiming it at Remus—who was crawling towards her as his face morphed into the long snout of a wolf—and waiting. She wanted to be sure the spell would take, and that meant waiting until the transformation was complete.

Remus screamed twice more but managed to crawl far enough that he was closer to Minerva than he was to Deasura before collapsing to the floor. When he looked back up, he growled, and Minerva flicked her wand. The water-breathing spell cast a jet of pale pink light and the wolf flinched away from it but not quick enough to dodge out of its path. Good.

'Come and get me, then,' she said, staring the wolf in the eyes. 'I'm sure I smell delicious.'

The wolf sniffed the air before turning his head to look at Deasura, growling and spinning around.

'Stupefy,' Minerva said, shooting a stunning spell at the wolf to draw its attention back to her and getting a yelp for her trouble. The wolf turned back to glare at her, growling deep in his throat. 'Don't you make me break my promise. Stupefy.'

The second attack did its job, and the wolf crouched, stalking towards her. 'That's it. A little closer. Come on.' She backed away as the wolf climbed the steps to the pool, moving closer to the underwater door leading out to the lake. The wolf seemed to hesitate at the edge of the water and Minerva cast another stunning spell at him—a little encouragement—hitting him in the face. The sound of pain the wolf made caused a pang of guilt in her chest, but it worked. With another growl and a shake of his head, he sprang at her and she dived for the door.

Holding a wand in each hand, she directed them behind her and cast a powerful wind charm from both simultaneously, propelling herself through the water. The lake was deep, dark, and bloody freezing. Several seconds passed before she was even able to see her surroundings, but once there was enough light, she glanced over her shoulder to make sure the wolf was following her. He was, looking eerie with his fur floating around him and bubbles streaming from his mouth as he paddled furiously with all four paws, creating impressive speed.

She was keeping ahead of him, though, and she turned her face back to the surface, angling her ascent so she would break through on the bank of the lake. As she neared the surface, she poured more magic into the spells, increasing her speed so that when she reached it, she shot into the air at a sharp enough angle that her momentum carried her over the land, transforming in mid-air to land on all fours in the grass. Not pausing for a moment, she broke into a run for the Whomping Willow.

Before Moony even opened his eyes, he knew he was not alone, and he growled a warning to whoever was there. It wasn't a packmate. He knew their scents now, and this one was different. He could tell it was one of the two-legged creatures, but there was a hint of something else underneath. Something more like him. Looking up, he growled again. He'd been right. It was one of them, and it had two creation sticks, one of which was pointed at him. The creature made a sound, and a light flew towards him, making him flinch back, but when it hit, it didn't hurt.

He wasn't in his usual space. This one was smaller and full of things that smelled like outside. He sniffed the air curiously, and that's when he smelled it. The dangerous creature was there too. He'd dreamt of his packmates—a strange dream that didn't make any sense at all—and woken with a strong sense that they didn't want him to hurt the creatures like them, but the dangerous creature wasn't like them. It looked like them, but Moony could tell it was different. And, oh, how he wanted to bite it.

He turned his head to look for it and found it laying unmoving on the floor behind him. Even better. It was already quiet and still. His packmates couldn't be upset with him for biting something that was already quiet and still. Turning fully, he growled in anticipation, but a moment later, a burning pain hit him in the shoulder, making him yelp. The other creature was using her creation sticks to hurt him. He turned to look, and she made some sounds and then another light flew at him, burning him in the leg.

His packmates would understand if he was being attacked, wouldn't they? He had to defend himself. The Fighter had made four of these creatures quiet and still when they'd been attacking the wolf, so it must be okay. Crouching, he stalked towards the creature, growling in an attempt to scare it away, but he paused at the top of the slope. The creature was standing in a small pool of water. Another light, this time burning him right in the face, was all it took to persuade him to get wet. He pounced, leaping at the creature, but it dived under the water.

Moony followed, swimming through a gap in the wall. Several seconds passed as he chased the creature up through the water, and his lungs were burning, desperate for air. Giving in, he gasped, only to find he could still breathe. The creature was only slightly ahead of him when it broke the surface and disappeared, but when Moony climbed out of the water, it was gone. The only living thing in sight was a small creature with a long tail, running away on four legs, and Moony stopped, confused. Where had his prey gone?

After shaking the water out of his fur, Moony looked around. In the direction the small creature had been running, there were trees, hundreds of them, all crammed together. It looked like the place he'd spent the day when he escaped, and it called to him. In the other, a stone structure towered over everything. There were square lights dotted across the front of it, and at the base, an opening. Standing in the opening were four of the two-legged creatures, and three of them were his packmates.

Knowing he shouldn't approach them if he didn't want to hurt them, he threw his head back and howled, but they didn't respond. Instead, they pointed their creation sticks at him, and suddenly there were two of him again. One standing next to the water, the other, laying in a moonlit clearing.

He wasn't afraid this time. The Fighter would come and take him to the place where he was first imprisoned. He would leave him there for a while, but then he would come back to his body. So, when the Fighter came, he followed, allowing himself to be locked into the small space, while the creature that hated him left with the Fighter. Then the wolf beside the lake disappeared.

Remus stared at Professor McGonagall standing in Emhio's pool in her underwear as his transformation came to an end, hoping with everything in him that she had a good plan. He closed his eyes as the transformation came to an end, and when he opened them again, he found himself in his childhood bedroom. It took him a moment to rid himself of the confusion, but then he realised Sirius must be casting the spell. What did that mean? Had Professor McGonagall failed? Had he mauled her and escaped the room? Was he loose in the castle?

There was nothing he could do while he waited, so he paced the room, looking out of the window occasionally for any sign of them, and then, after what felt like a lifetime, he heard the key turning in the lock and he turned to face the door.

'What's happening?' he asked the moment the door swung open.

'In you go, Moony. Good boy,' Sirius said, as the wolf obediently entered the room, jumping up onto the bed and curling up in a ball. 'Quick as you can, Remus. Minnie led Moony out through the lake. He's on the bank right now.'

Remus nodded, already following Sirius out of the room. 'Storm?'

'I'm sorry. I don't know,' Sirius said, locking the door behind them and triggering their transportation to the moonlit clearing. 'Is it working?'

'Yeah,' Remus said with his mind projection. His real self just growled from within the body of the wolf. Oh, this was weird. He knew how it felt to be the wolf, of course. His consciousness was the last thing to go when he transformed, but he'd never been the wolf without being in extreme pain before. This was the first time he could truly appreciate the experience. He had four legs and a tail, which he wagged, just to see if he could. It felt kind of nice, so he did it again.

Then he remembered he didn't have much time, but before he could even get his bearings, a cat stalked right up to him and bopped him on the nose with its front paw. What the fuck? he tried to say, but all that came out was a series of barks, and the cat sprinted away. The wolf's instincts pushed him to give chase, and he was running before he'd even thought about it. When he realised and thought about the process of running with four legs, he stumbled, tripping over his own feet and a moment later the cat stopped, turned and walked back up to him, bopping him on the nose again with an expression that looked exasperated. Remus sniffed the air, and the cat smelled exactly like a cat, but it wasn't. It was Professor McGonagall. Of course, it was. The markings around the cat's eyes looked exactly like her glasses.

Climbing back to his feet, he yipped, and broke into a run again, trying not to think about it too much, just allowing muscle memory to figure it out for him. Professor McGonagall darted ahead of him, running straight up to the trunk of the Willow and pressing her paw against the knot that would freeze the tree. She waited there, keeping the tree still, until he was close enough, and then she jumped down into the hole hidden in the trunk. Remus followed.

They ran down the passage together, and when they reached the end, Professor McGonagall sprang up through the trapdoor, using the ladder as a halfway point, and Remus stopped, sitting back on his haunches. He wasn't sure he could make such a big jump, but he had to try. He wasn't sure how long he had left.

Professor McGonagall's feline face poked itself over the edge of the opening and looked down at him, mewling, and everything went black.

When Moony flashed back to the clearing for a second before returning to his own body, he found himself somewhere new. He was surrounded by dirt, sitting on his haunches, and staring up at an opening above him. The small creature was looking down at him, so he yipped and jumped up to join it, scrabbling on the wood to clamber inside. It was his space. The opening he had jumped through was the floor shape that usually separated him from his pack—he'd known that was the way out.

The dream he'd had where he was able to communicate with his packmates was still strong in his mind. It felt like a dream, but also more than a dream. It felt true. He wasn't just a wolf, but half of something else, and he was dangerous, which is why he was supposed to stay in here until his packmates could make it safe for him to come out. He didn't know why the other half of him, the creature that hated him, hadn't come here before he changed, but he was here now, so he walked further in, away from the opening that led outside, and lay down, looking at the creature sitting next to the opening.

It mewled again, before jumping down the hole, and a second later, the opening slammed closed with a bang, which was quickly followed by a click, and Moony was alone.

When Sirius shot off towards the entrance doors, Regulus followed him. It was so sudden, but that was nothing new for Sirius. He often acted impulsively, with no warning. Regulus was used to it. What he wasn't used to was the sight of his Transfiguration teacher shooting up out of the lake in her underwear and transforming into a cat, closely followed by a werewolf. He would admit to being a little impressed, though. That took a hell of a lot of daring.

James and Peter had joined them on the threshold, and they all watched as the wolf shook himself off before turning to look directly at them.

'Shouldn't we close the door?' Regulus asked as the wolf threw his head back and howled at the moon. 'I realise that's your friend, but he's still a werewolf. He can probably smell us, even at this distance.'

'No, we need to help,' Sirius said. 'Are you ready?'

'Ready for what?' Regulus asked at the same time as James and Peter pulled out their wands and said. 'Yep.'

'Just stay there and be quiet,' Sirius said. 'I need to concentrate.'

Regulus swallowed his retort and snapped his mouth closed. If Sirius and his friends knew of some way to control a werewolf—and since they were friends with one, it seemed prudent for them to have learned a way—then he did not want to prevent them from utilising it.

The wolf didn't move as Sirius started a chant-like incantation combined with intricate wand movements, and Regulus could detect no change in its demeanour which was currently non-threatening and almost curious, making him wonder if it had ever been outside before. Probably not. Remus seemed like a responsible kind of person, even if he did choose Sirius to be his best friend. Which begged the question of why he'd been strolling through the dungeons so close to moonrise. Even if Regulus was grateful that he had been—he'd probably be dead otherwise—it seemed like an extremely risky thing to do.

Several seconds passed with Sirius' chanting, and then Peter lifted in his own wand and cast something with a long incantation and more complicated wand movements, immediately followed by James. When James finished, they all dropped their wands to their sides.

'Did it work?' James asked.

Sirius nodded. 'Yeah, that's Remus in control now.'

'Did McGonagall just bop him on the nose?' Peter asked with laughter in his voice. 'Bloody hell, she's got nerve.'

Regulus looked back to see the wolf was now chasing Professor McGonagall towards the Whomping Willow, and he held his breath. Surely she wasn't planning to let the tree beat him to death? But no. When she reached the trunk, the tree froze in place and a few seconds later, the wolf ran towards it and vanished.

'Where did they go?'

'There's a passage under the tree. It's where he goes to transform,' Sirius told him, taking a step outside the door.

'So, we're safe now?'

'Should be,' James said, grabbing Sirius and hauling him back inside. 'Depends if the spell lasts long enough for McGonagall to get him into the room at the other end and shut the door.'

'Even if it doesn't,' Peter said, 'Moony might cooperate. He didn't look like he wanted to attack us even before the mind magic.'

When Regulus looked at him, Sirius was clawing at his chest with one hand and his eyes were damp with tears. 'Are you okay?'

'Not really, no,' Sirius answered, his voice sounding strained. 'Let's try to get to the Hospital Wing first, but I may need to take you up on that Stunner soon, Bubbles.'

'Will someone tell me what's going on?' Regulus asked. 'And for Merlin's sake, why does everyone you know have to have a bizarre nickname?'

'Distract me, Reggie. What happened with you and Professor Tenebris?'

'I don't remember much,' Regulus replied as they turned away from the door and started towards the stairs. 'I was going back to the common room after returning my library books and I saw her in the corridor coming towards me. It's fuzzy after that. I think she cast the Imperius curse on me. I remember following her to the room you found me outside, and then she bit me. She's a vampire, apparently. I couldn't do anything to stop her. It was awful. I just stood there and let her drink my blood. I remember noticing Remus at the door and hoping he would help.'

'Wait. She's a vampire?' James asked. 'Did you know she was a vampire?'

Peter shook his head. 'Not a clue.'

Sirius nodded. 'Yeah, Remus told me. I didn't think she'd ever feed from a student, though.'

'Anyway,' Regulus said, cutting them off as they reached the second floor. 'She let me go when she saw Remus. They duelled for a while and I just stood there watching, but then Remus shouted at me to fight, and I thought "why am I not fighting?"'

'Then what happened?' Sirius asked, his voice tight with pain.

'I fought. When I broke the spell, she was casting the Imperius curse on Remus. She told him to leave and go to the Shack? Is that where he is now?'

James nodded. 'The Shrieking Shack in Hogsmeade.'

Regulus didn't know anything about a Shrieking Shack in Hogsmeade. He'd never been to the village. But he nodded anyway. 'So I stunned her.'

'How did you manage that?' Peter asked. 'She's so fast.'

Regulus shrugged. 'She had her back to me, and probably thought I was still Imperiused.'

Sirius huffed a laugh. 'You shot her in the back? That's my little brother.' If Regulus didn't know better, he'd think Sirius sounded proud.

'How you doing?' James asked as Sirius started slowing down near the top of the third set of stairs.

'It's agony, quite frankly,' Sirius said. 'But I've had worse.'

'You don't have to do this. We can stun you and carry you there.'

'What is going on?' Regulus demanded, refusing to be kept in the dark a moment longer. 'What's wrong with him?'

All three of them exchanged glances full of meaning, and Regulus lost his temper. 'For fuck's sake. Will you just tell me? What do you think I'm going to do? Go running to Mother? Don't you know me better than that?'

Sirius nodded at James, which apparently constituted permission because James started to speak. 'We cast a spell on ourselves. A permanent one. It lets us know when one of us is in danger and leads us to them, but it doesn't stop until you're close enough to touch them. Sirius is linked to Remus, and he used the spell to find him earlier.'

'But he didn't get close enough to touch him, so… What? The spell is punishing him?'

'It's insisting I keep my vow to protect him,' Sirius said. 'It's really not happy that I'm moving further away from him.'

'That was a really stupid thing to do, even for you.'

'Yeah,' James said. 'We realised that after we'd done it, but by then it was too late. It's irreversible.'

'Saved someone's life tonight, though,' Sirius pointed out. 'Not that she deserved saving, but Remus would have been distraught if he'd killed her.'

'It wouldn't have needed saving at all if you'd all listened to me and made Remus go to the Shack,' Peter said.

'If Remus hadn't come, I'm pretty sure I'd be dead,' Regulus said. 'How did he know we were in there, anyway?'

'Probably smelled you,' Sirius said.

'Well, that's creepy.'

They'd reached the doors to the hospital wing and James went in first, holding the door for everyone else. Madam Pomfrey left her office at the sound of visitors, and her eyes widened when she saw who it was.

'What's happened?'

'A lot,' James replied. 'But the main thing is Regulus was attacked by a vampire.'

Her eyebrows went up. 'A vampire? In Hogwarts? Are you joking, Mister Potter?'

'No. It was Professor Tenebris.'

'Come and sit down, Mister Black,' Madam Pomfrey said, indicating a bed before turning back to James as Regulus walked over to her and took a seat. 'Professor Tenebris is a vampire?'

'Apparently,' Regulus said, tilting his head so she could see the wound on his neck. 'She Imperiused me so I couldn't escape and took me to… I'm not sure. It was a classroom with a dry swimming pool at the front?'

'It was Professor Hawthorne's old classroom,' Sirius said. 'Is he going to be okay?'

'He'll be fine,' Madam Pomfrey said. 'I'm just going to take a sample of the magic in the wound, then I'll heal it up.'

The wound tingled as she did whatever she was doing. Regulus couldn't see, but then the area felt warm for a second and the pain disappeared. 'Thank you.'

'You're quite welcome, dear. Wait here while I fetch you a Blood Replenishing potion.' She bustled away into her office and Regulus looked up. Peter and James were now on either side of Sirius, forcibly holding him in place.

'Is it getting worse?'

His lips were pressed tightly together and Regulus could see the strain on his face, but he nodded.

'It's going to keep getting worse until morning, and that's hours away. You need to let us stun you,' James said. 'You're being ridiculous.'

'I need to know if Professor Tenebris is okay first. So I can tell Remus when he wakes up.'

'Where is Professor Tenebris?' Madam Pomfrey asked, returning from her office with a vial of ruby-red potion, which she handed to Regulus.

Stunned in Hawthorne's old classroom,' James answered. 'Unless Professor McGonagall already went back.'

'Back?'

James nodded. 'Remus found them when he was on his way to the Shack for the night, and fighting her took too long, I guess? He transformed in the classroom and Professor McGonagall led him out through the lake.'

'She…' Madam Pomfrey paled. 'Was she… did he…'

'She's fine, from what we saw,' James said. 'Moony wasn't interested in her after she changed into a cat.'

She nodded and then seemed to notice Sirius' predicament. 'And what's wrong with you, Mister Black? Are you hurt?'

'He used the tracking spell to find Remus earlier, but he didn't get close enough to cancel it,' James said, answering for him. 'The spell causes pain when you don't follow its directions.'

Madam Pomfrey tutted. 'Why didn't you mention this sooner? Come and lay down, Mister Black. I'll be back in a moment.'

'Wait, she knows about the spell you did?' Regulus asked as James and Peter dragged Sirius over to the bed. He seemed to have enough willpower to stay put, but not quite enough to move further away from Remus without assistance. How much of his tolerance for pain was due to the torture he'd endured the previous summer, Regulus didn't know, but he was willing to bet it was a large part of it.

'She found out at Easter,' James said, helping Sirius onto the bed with a huff. 'Minnie and Dumbles know too.'

'A little more respect for your professors, please, Mister Potter,' Madam Pomfrey reprimanded, returning from her office again, this time with a shiny silver disc in her hand.

'It's affectionate,' James replied with a bright smile.

'Nonetheless.' She strode across to the side of Sirius' bed and placed the silver disc on his chest, hovering her hand over it and muttering under her breath. The disc glowed with a pale blue light which spread out across Sirius' chest and then expanded to cover his whole body. For several seconds after Madam Pomfrey stopped, the light pulsed and then, all at once, it disappeared and Madam Pomfrey picked the disc back up. 'How do you feel now?'

Sirius sat up with a grin. 'The pain's stopped! What is that? And can we keep it?'

Madam Pomfrey chuckled and pocketed the device. 'It would be useless to you without extensive medical training. It's a magic dampener. I wasn't sure it would work, but since the spell is so tangled up with your own magic, I thought it was worth a try. You won't be able to perform magic for twenty-four hours.'

'What? You could have told me that before.'

'It's just one day, Mister Black.'

'But I have to go home in the morning.'

'Well, that works out well then, doesn't it? Since you're twelve years old, and shouldn't be performing magic at home, anyway.'

'Yeah, of course,' Sirius said, waiting for Pomfrey to look away before shooting Regulus a panicked look. If he had to perform magic and couldn't, he'd be punished for it. Regulus gave him a nod—yes, I'll cover for you. Don't worry—and Sirius smiled at him, relieved.

'Oh good, you're all here,' Professor McGonagall said, entering the Hospital Wing with Professor Tenebris floating ahead of her on a stretcher. Thankfully, she'd managed to locate robes on the way there and was fully clothed again.

'Is Remus okay?' Sirius asked immediately, swinging his legs off the bed.

'He's perfectly fine.' Madam Pomfrey hurried over to help Professor McGonagall transfer the still stunned vampire into a hospital bed and then she vanished the stretcher, turning to face Sirius. 'He followed me in and laid down so I could leave and shut the door.'

Sirius let out a heavy breath. 'Thank Merlin.'

'Thank McGonagall,' James said, giving Sirius a significant look before turning to beam at the teacher in question. 'You were incredible.'

'You weren't supposed to be watching.'

'The tracking spell dragged Sirius there. He couldn't help it, and we had to stop him from going any closer.'

'I'm okay now, though. Madam Pomfrey fixed it,' Sirius said. Then he nodded his head to indicate Professor Tenebris. 'What's going to happen to her?'

'The Aurors will need to be called in. They'll take statements from everyone who saw her attack you, Mister Black,' Professor McGonagall answered, looking at Regulus when she said his name, 'including yourself.'

'That's just me and Remus,' Regulus said.

'And then she'll likely be executed.'

Regulus frowned, looking at his unconscious teacher. He'd learned a lot from her that year, and she'd always made her lessons fun and interesting, unlike some teachers he could mention. She would have killed him if Remus hadn't arrived, he was quite sure of that. But still, he didn't want her to die. 'What if I refuse to give a statement?'

'You don't wish to report the crime?' Professor McGonagall asked, raising an eyebrow at him.

'I would like to know why she did it before I make that decision. Is that okay?'

'Yes,' Professor McGonagall said. 'I think we can make that work if she's willing to talk. I've already asked the Headmaster to join us. He should be here shortly, then we'll wake her up.'