Calla was sure that, to any outsider who were to happen upon them in the tunnels, they would have looked a very strange group indeed. Up front was Crookshanks, bottle-brush tail bobbing as he led them through the shadows; he was followed by Remus, who was cuffed tightly to Pettigrew, who was still sniffling, and who was cuffed on his other side to Ron, with his strapped leg. Snape floated eerily just behind him, held afloat by Sirius pointing his wand at him, and Calla was sure a couple of times that he bumped his head or feet, it was deliberate. She followed at the rear, Matilda held tightly in her arms, with Harry and Hermione either side of her.

They all had to squeeze very awkwardly back into the tunnel, with Remus, Pettigrew and Ron walking sideways to manage it. Snape's head hit the ceiling as Sirius guided him through. Harry hurried on after him, falling into step, and Calla kept a close eye on them, catching their conversation.

"I don't know if Remus might have told you this, Harry," Sirius said. "But I'm your godfather."

"Yeah," she could hear Harry saying. "I know."

"Your parents," Sirius went on, "Before they died, appointed me as guardian of both you and your sister, should anything... Happen to them. I know you've been living with your aunt and uncle and I understand if you want to stay living with them - I presume that's why you haven't been with Remus all the time - but should you ever want to... Both of you, Calla too, of course."

"Leave the Dursleys?" Harry asked quickly. He sounded like he could hardly believe it, and Calla couldn't believe it either. They'd wanted for so long to leave, for them to be allowed to stay with Remus and here Sirius seemed to be suggesting they stayed with him. Just as easy as that.

"Of course I understand if you wouldn't want to," he went on, and Calla picked up her pace, getting closer to hear, "but we could arrange for visits, some with me, some with Remus-"

"Are you mad?" Harry asked. Calla could see he was beaming. "Leave the Dursleys'? We've been wanting to leave forever, we were never allowed to live with Remus! Of course I'd want to live with you!"

"You - you mean it?"

"Yes, I mean it! Have you got a house? When can we move in? Can - can Remus stay too, we could all be together!"

Sirius' face broke into the first true smile Calla had seen from him. It was bizarre; the years seemed to fall away from him in a moment, and he could have been a much younger man, blazing with happiness. "Calla?" he called down the tunnel, and she startled, running on ahead and pretending like she hadn't just heard everything.

"Yeah?" she asked, bounding to Harry's side. "What's wrong?"

"Nothing," Sirius said, beaming. "Harry and I were just speaking-"

"We can move in with Sirius!" Harry said happily. Calla saw Remus' head turn back towards them, pale in the tunnel's dim light.

She stared at him. "But... We have to stay at the Dursleys'. Dumbledore wouldn't let us leave."

"I'm your legal guardian," Sirius told her, which she knew, and it didn't make it any better. She felt something sour in her chest, as her gaze flicked to Remus. He was pretending like he hadn't heard, but she knew he had. "If you want to stay with me, Dumbledore can't stop you."

"But..." She swallowed. "What about Remus? Harry, we've always wanted to stay with, all of us have been trying to let that happen."

Sirius shifted awkwardly. "We can arrange that, for Remus to live near or whatever suits him. But - but would you?"

"What? Move in... With you?" Calla stared at him. She wanted to leave the Dursleys so badly, but they'd just met Sirius and only just found out he wasn't a mass murderer responsible for the deaths of their parents and she'd much rather stay with Remus, if she could. Not that she could bring herself to say so in front of Sirius, who looked like he was smiling for the first time in years, or Harry, who seemed to be absolutely beaming. "I - I'll have to think about it."

Sirius' expression fell a little. "Of - of course. I couldn't expect you to make up your mind immediately. But... The offer's there, if - if the two of you do want to."

They didn't say anything more as they continued on up the long tunnel. Calla hung back a bit, walking slowly with Hermione, who was looking at her curiously. She shifted uncomfortably and tweaked an awkward smile, turning to focus her energy on stroking Matilda.

Once they reached what must have been the end of the tunnel, Crookshanks darted up, and pressed the knot to still the Willow. Remus, Ron and Pettigrew clambered up in a clumsy, awkward way, but they managed to reach the ground in one piece, with no sounds of a scuffle with the tree. Sirius sent Snape floating up through the hole by the roots, bumping his head against the soil as he did so. He still seemed to be grinning as he climbed up himself, finding solid ground. Harry disappeared up next, then Hermione, who Calla passed Matilda too before she clambered out of the hole herself.

The whole world outside was pitch black now, and it was cold. She checked her pocket for the Invisibility Cloak and her wand, before she took Matilda back into her arms and hurried out of the tree's reach. The only lights out here now were those coming from the castle, which still seemed ages away. Up front, Pettigrew was sniffling and whimpering, still muttering things Calla couldn't hear.

Harry seemed lost in thought, and Calla went up the slope in a determined silence. Her mind was fizzing with possibilities. If Pettigrew was found guilty and Sirius free, and if he argued for them to stay with Remus, they'd surely be allowed to. But the likelihood of that happening and Sirius not wanting them to stay with him... She looked forlornly at Remus. How were they going to figure this out?

"One wrong move, Peter," Remus was saying, still pointing his wand sideways at Pettigrew.

They made their way through the grounds in silence, Calla soothing Matilda, who was shaking a little, likely from the trauma of earlier on. Pettigrew was still whimpering and Snape was still hovering limply in the air, and lolling forward so that his chin hit off his chest.

And then the clouds above them parted, smoky grey against the blue of the sky, and a chill came over Calla. Silver shone from behind the clouds; the silver of the full moon. "Remus," she said quietly. He didn't move, but stopped walking entirely. Calla dashed forwards. "Remus."

Snape's feet collided with the back of Ron's head, and Sirius held out an arm to hold back Harry and Hermione. His other hand fell against Calla's wrist as she moved forward. "Remus!" He'd gone completely rigid. "No. No, no, Remus. Your potion!" He began to shake all over, and Sirius grabbed her by the arm, pulling her back.

"Run, Calla," he said.

"But Remus - and - and Ron-"

"Leave it to me," he said, even as she ran forward, trying to grab Remus, trying to do she didn't know what, but trying to do something. She could hear footsteps rushing away, her brother shouting for her.

Remus' head was lengthening as it happened, and he snarled, as all his limbs trembled. "Remus!" His shoulders hunched over, and fur sprouted from all over, his arms swinging out, fingers lengthening into sharp claws. Footsteps rushed towards her, Sirius' hand closing around her forearm as Remus - no, the wolf- lashed out, claws catching on her arm. She hissed as Sirius dragged her away.

"Run!" he insisted, and a second later, as Calla stumbled down the slope, he had transformed back into that massive bear and was lunging forwards. Ron whimpered as the werewolf shook, twisting and breaking free of his bonds. She shrieked as the dog tackled the wolf to the ground, hauling him back and away from Pettigrew and Ron.

Hermione screamed as Pettigrew lunged for Remus' wand which had fallen into the ground, and Calla ran forwards again. "No!" she yelled, but he was closer than she was. Ron tipped over, falling onto his bandaged leg, and Calla rushed to his side.

BANG! She and Ron were both blown backwards, and she landed hard on the ground, coughing. "Expelliarmus!" she hear Harry shout, and there was a burst of red light. She struggled to her feet, staring around, trying to find Ron. "Stay where you are!" Harry bellowed to Pettigrew, pointing Remus' wand back at her.

"Ron!" she shouted, stumbling over her own feet. "Ron!" She stumbled, not able to see properly, in the vague direction of the forest. "Ron!"

"Sirius!" Harry yelled. "Sirius, he's gone!"

"Ron!" Calla yelled again, finding herself running over a rocky slope.

There was a growl somewhere near her and she leapt back. "Calla, the wolf!"

She didn't know where to go; she ran and ran, as if she could outrun a wolf. They couldn't climb trees, could they? "Calla!"

She panted, hiding behind a large boulder, as she saw something like the wolf streak past, followed by the dark shadow of a dog. Calla lay her forehead down against the cold stone, breathing heavily. Remus - the wolf. And Pettigrew, had he gone? Had he transformed, was that it? It was all over.

She gritted her teeth, pushing back to her feet, and illuminated the tip of her wand. She had to find that rat. "Calla!" Harry was yelling, as she stumbled over grass and stone, eyes peeled.

"I'm fine!" she yelled back at him. "I have to get the rat!"

Her foot caught on a large stone and she let out a yell, blinking as something like a rat flew past. Scrambling to her feet, Calla followed it, lunging towards the ground. Her wand went flying and she sprawled over the grass as she clamped the little, squealing rat in her hands. It's squealed as she got up, trying to spot her wand, but it was hard to look for or try and grab with a writhing rat in her hands. "Harry!" she yelled. "Down here! I-"

The rat bit down hard on her finger and she screamed, trying to catch ahold of its tail as her hand stung, burning where the rat had bit it. "You're not getting away that easily," she hissed, as Matilda leapt up, catching the rat's tail between her teeth. "Don't kill it!" she insisted, scrambling for her wand. "Harry!"

There was a yowling sound coming from somewhere below her, in the distance. Like a dog in pain. Her heart leapt into her throat and she signalled to Matilda, rushing down the uneven slope. "Sirius? Remus?"

She turned as Matilda ran to her feet, rat scraping the grass. "Harry!" she bellowed up the slope, but he was nowhere. There was no reply but the rustle of trees. "Harry! Hermione!"

There was a burst of light, something blazing hit Calla's shin and she stumbled back, falling to the ground. Matilda yowled, and Pettigrew grew back to full form, sending Matilda soaring across the grounds. "You-" she yelled, but she was too slow in getting to her feet. He turned back to a rat, and she lost him in the darkness. "Matilda! Matilda! Harry!"

There was a dark, indistinct shape shooting ahead in front of her and she huffed, brushing hair from her forehead and her cheeks. At some point it had gotten something sticky in it, possibly blood. She scrabbled for the bobble on her wrist and took off at a run, tying her hair up into a very hasty, very messy bun, a ponytail folded under the elastic. Her feet pounded over the grass, following only her instincts, not any sort of light. "Matilda!"

There was no reply but what might have been a purr, somewhere in front of her. She sprinted after it. "Calla!" Harry's voice was yelling somewhere, and she slowed, but she was still running, eyes following Matilda, or what she thought was Matilda. If she led her to the rat... "Calla! Sirius!"

"I'm fine!" she called back, with no idea if Harry could hear her or not. A branch scraped against her arm as she ran towards the forest, sweeping the rest of her hair down the back of her robes, tucked in so it wouldn't catch. There was a light coming from somewhere, she realised, and it was enough to slow her steps.

She paused, panting, at the edge of the forest. Matilda had disappeared. She was all on her own; she couldn't even see Hagrid's hut, only the very distantly twinkling lights of Hogwarts Castle. All alone. Suddenly it didn't seem like such a good idea to go tearing off. "Stupid rat," she muttered, bending down and scouring the ground. There was a noise from within the forest, the sound of a twig snapping.

She advanced forwards, a hand on her wand, just in case. She had to be quiet, stealthy, unseen. Of course. Calla took the cloak from her pocket, sweeping it over her, and moved onwards through the forest floor. This was a terrible idea, she told herself, but she kept moving. Her brother's voice was muffled in the distance.

Something snapped to her right. There was a movement, a streak of white, almost like a wing. She turned, staring, and then heard a strange squealing sound in the other direction.

She turned that way, eyes fixed on the ground. That had to have been the rat... But her stomach was very uneasy. She wasn't certain at all, and she could feel it slipping away. Through the mass of trees, she could see the light again, silvery, like the reflection of the moon on the lake. But... She shook her head. It felt wrong; cold wrapped around her suddenly, and she turned, stumbling back, gripping a tree. No.

"Calla! Calla!"

That was her brother's voice, coming from the same direction as that light. But she was sure... There was something else there, something she could feel just at her shoulder, like a hand, settled, trying to pull her back. She whipped around, but there was nothing there; only darkness and the cold. She took her wand out, trying to illuminate the space between the trees. "Lumos," she whispered, but it only fixed brightness out the end. "Come on," Calla muttered, shaking the wand as if that was the problem. "Not now, for God's sake! Lumos."

Nothing. But there was - there was a hand, something pale and yellowing clawing around the edge of a tree. She shook her head, squeezing her eyes shut. It wasn't a vision, but it wasn't real. She was sure it couldn't be real. The dying hand. "Lumos," she whispered again. She had to see what this was, had to understand. The white light flickered between two trees, showing skeletal fingers.

Something cold pressed in at her back. Mine, that familiar voice whispered, and she gasped, breath catching as she choked on it. She grabbed a tree, leaning on it heavily. "What are you?" she whispered, still terrified of the answer. "Who - who are you?"

I will take what is mine, said that hoarse and rasping voice. Stand aside, girl. Give up. You cannot stop me.

"Calla!" Harry's voice yelled again, breaking out of her trance. She turned around, tripping over a twig, and sprinted out of the forest, towards the shining light of the lake. It was freezing as she ran, though her heart was pounding so hard she barely noticed, and barely noticed why.

She panted as she came out onto the lake's shore, stuffing the Invisibility Cloak hastily back into her pocket, as she saw Harry sitting there, with Hermione, both of their wands outstretched towards the lake. Sirius was between them, hands over his head. "Harry!" she yelled, eyes latching onto the lake. The mass of darkness coming over the lake... She shuddered, cold gripping her again, so intense it felt like it would never leave her. "Harry!"

She ran forward, dropping down to her knees beside him. "Expecto patronum," he was muttering, a feeble silver light wisping out the end of his wand. Hermione was saying the same, forehead creased, and she was pale, shaking. "Expecto - Expecto patronum. Calla..."

She grasped her wand tightly, heart hammering, forcing her to think of last year. Beating Riddle. She could save people, she told herself. Things didn't have to end the way she saw them. "Expecto patronum," she said as loudly as she could, wishing the Dementors away. "Expecto - Expecto-" her breath snagged in her throat "Expecto patronum!"

One feeble wisp came out the tip of her wand. "Expecto patronum," Harry repeated, voice rasping and raw. "Expecto patronum!"

She was going to be safe. She had to be safe. She squeezed her eyes shut, willing herself to see a future she didn't know was real. "Expecto patronum!" she shouted.

"He's innocent," Harry was rasping, as a Dementor came nearer to them. Underneath its hood was a grey l, scabbed sort of face, skin stretched tightly over empty eye sockets. "Expecto -"

"Expecto patronum-" Calla shouted. It'd be okay, they'd be okay, she could save them, she had to be able to save them. She grabbed her brother's hand, wishing and wishing she could keep the Dementors at bay.

But their breath was rattling louder and louder. A slimy, cold grey hand reached out and took her fingers, prising them away from her brother. "Harry," she rasped. "Harry, it'll - it'll be alright. It - it has to... Expecto patronum."

But nothing was happening. She didn't know how she could have expected anything to happen. A Dementor's claws dragged over her shoulder, freezing to the touch. Her wand slipped from between her fingers. She couldn't do it. She couldn't do anything. She was stupid to think she ever could, that she was ever able to. She couldn't save them. She couldn't do anything. She couldn't even save herself. She was weak.

Stupid girl, the voice echoed in her head. You cannot stop me.

She heard a scream - her mother's scream - and a flash of green light seared across her vision. Her scar burned and panic rose in her stomach, her chest, her throat, taking over everything. She could hardly breathe. The rat flashed in her mind's eye, she could hear laughing, a skeleton rattling and its hand clamping down on her shoulder. "No," she whispered, the truth setting in. She couldn't stop it. "No, no, no!" The rat was slipping away, further and further, slipping through her fingers as she sat by edge of the lake, chest hollow and head on fire.

"Expe-" her voice fizzled out as the cold replaced the burning feeling, gripping her heart. It battled her down her like a hailstorm and she sank, head hanging lowly, reaching for Harry.

Clammy hands wrapped themselves around her neck, forcing her chin up. Rattling breath drew closer and she squeezed her eyes shut, cringing away. No, no. It couldn't, no. She tried to scramble away, but the Dementor's grip was like a vice. She had no wand, nothing to defend herself with. Her arms fell limply at her side. All the warmth rushed out of her.

There was a last, muffled cry of expecto patronum as she sank down to the ground, felt sharp nails against her throat, heard her mother's scream and that awful voice's hissings, and she shouted for her brother but had no idea if he was even still there.

Her eyelids fluttered, and she caught only a glimpse of a silvery light as she fell, the Dementor's hands slipping away. Her cheek landed on her arm on the ground, and she reached out a hand, forcing her eyelids open as Harry fell, too, and she reached for his hand. The cold was ebbing away, ever so slightly and ever, ever so slowly. The Dementors ... They were leaving. She forced her eyes to open, straightened her glasses, to see the silver light dying on the lake.

"Harry," she croaked, fumbling for his hand, stumbling to her feet. She fell back down again; it was like her every strength had been sucked out of her. Her eyelids closed and she curled in on herself and her empty, cold, rattling chest, and the last thing she remembered was crying.