A/N: Hmm, since I get this big a response from one little cliffie, I think I shall give you another one. Hope this update is quick enough for you and thanks for all the reviews - they're very much appreciated. Enjoy.

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Chapter 36 – Darkness and light

Harry blinked.

Then he blinked again.

The darkness remained.

Slowly, feeling his way with his hand, he sat up and managed to locate his wand. He lit it and scanned the area around him cautiously, afraid of what he'd find. The last thing he remembered was someone grabbing him by the collar and hurling him into the arch of darkness, and then he was falling and then...and then?

The light from his wand found a leg, clothed in dark jeans. Who had been wearing jeans?

He scrambled over and the light illuminated jet black hair falling over a white face. He nudged Katherine and she raised a hand to shield her eyes from the light.

"Are you ok?" he asked, lowering his wand.

"I think I've dislocated my shoulder."

"Oh."

"You're going to have to put it back."

"What?" he stared at her and she sat up, wincing. "I can't do that."

"Well there isn't anyone else around, so you're going to have to."

"Can't we find the oth-"

"Harry, this really hurts." Harry looked at her for a moment, then nodded, swallowing hard.

"Ok. What do I have to do?"

"Pull my arm; it should just sort of, pop back into place."

"Are you sure?"

"No, but exactly how many physiotherapists do you expect to find down here? Just try it. Please?"

"Which arm?"

"Left."

Harry put down his wand and did as she instructed, trying to not grimace as he felt the joint slid back into position. Katherine let out a deep breath and Harry heard her fall back onto the floor. He reached for his wand again and lit it in the darkness.

"Ok now?" he asked quietly. She nodded, eyes closed.

"Yes. Thanks."

"Can you move it?" She wiggled her fingers gingerly.

"A bit. Probably needs strapping up. Have you seen the others?"

"No. We did all make it, didn't we?" One blue eye opened and looked up at him solemnly.

"Must have."

"Must?"

"Robert's got a five year old daughter and I can't go telling Cass I've got her husband killed. She'd never forgive me. Don't much fancy seeing Remus' face if Weasley or Granger snuffed it, either." She grimaced, sitting up slowly, feeling her left shoulder tentatively. "So yes, they must be alive. They can't not be."

"Right. Just a matter of finding them, then." He scanned the surrounding area with his wand and found they were in some sort of stone tunnel, carved out of the rock. The tunnel seemed to start where they were sitting and stretched away in front of them beyond the reach of wandlight. He wondered how they got there – he certainly recalled dropping quite a long way yet there was no hole above them that they could have fallen through.

"It sealed itself." He looked around to see Katherine watching him.

"Can we get back out?"

"Not this way." She stood and reached above their heads with her good arm, tracing her fingertips lightly over the rock. "One way ticket, I'm afraid." She glanced at him, apparently trying to decide something, and then nodded her head upwards. "Put your hand up."

"There's magic there?" he asked, with more than a little scepticism in his voice. She tilted her head to one side, thinking about it.

"Not exactly. Magic residue. That's what it is. Feel." He reached up uncertainly, touching the cold rock, but she shook her head. "Not the rock, just below it." He looked dubiously at her but lowered his hand slightly, fingers hovering a few millimeters away from the low ceiling of the tunnel.

"I don't-" And then he felt it. A peculiar sensation, like a million tiny strands of smoke brushing against his fingertips. "That's magic?" He half smiled at her expression. "Sorry, magic residue."

"What do you think?"

"I think you're going to say it's air currents, and it means we're about to get burnt to a crisp by a magma flare or something," he said, letting his hand fall to his side and looking challengingly at her. Katherine laughed, eyes glinting wickedly.

"Sorry to disappoint you, Potter, but there isn't much magma under London – not at this depth, anyway."

"So it is magic residue?"

"Yes. It's fading, but judging by the rate of decay, we haven't been down here long. Not if it sealed up right after we arrived, anyway."

"You could have just checked your watch to find that out," said Harry, peering at his own one.

"I broke it when I landed," answered Katherine, peering into the deep darkness that lay ahead of them. "I wonder why it split us up," she added, almost to herself.

Harry glanced at her, realising she'd changed the topic then looked back at his own watch, leaving her to her musings. Then he frowned, tapping it uncertainly.

"It's stopped."

Katherine looked round at him, then bent down and felt on the floor for her satchel.

"I don't think it's just your watch. No muggle technology seems to be working down here; no doubt that's deliberate."

Harry looked at the dead torch in her hand without really seeing it, his brain still catching up with the last thing she'd said.

"What split us up?" he asked abruptly, looking expectantly at her.

"The gateway," she answered, lifting the bag gently onto her right shoulder and pulling out her own wand. "Must have. I was holding onto your two friends when I went through, then they got pulled away from me, and the next thing I know, you're shining a light in my face and my shoulder's hurting like the blazes."

"Pulled away?"

"Yeah, different directions too. That's not good." She sighed heavily and glanced back at him. "Come on then. Can't go back, so the only option is forward."

"Why would it spilt us up?" asked Harry, falling into step beside her.

"Don't know. More importantly, why keep us two together? What have we got in common that the others haven't?" She waved her wand in a complicated shape and a softly glowing golden orb flew from it's tip to hang in the air before them, lighting the way. Harry put his own light out and tightened the hold on his wand; if something was waiting for them he was going to be ready for it.

"Orphans?" he ventured, in answer to her question.

"But I'm not an orphan, not really," she said slowly. "If that was it, you'd have woken up with Robert beside you, not me. Might be something to do with family, though. I mean, there's only so many ways you can divide people with spells."

"But we're not related," objected Harry, giving her an odd look.

"Not through blood, but you can speak Parseltongue, Harry, and you shouldn't have been able to feel that magic, not at your age, not without practice."

"What are you getting at?" asked Harry, starting to feel slightly uncomfortable. Katherine glanced sideways at him.

"No Gryffindor has ever been able to commune with snakes before. That's a Slytherin trait – not because it's evil, it's not, but because Salazar was a Parselmouth. It's his descendants that can speak it, and you are not his descendant, believe me. There are only two known descendants of Slytherin left on earth and I'm one of them. I'd know if you were."

"You think my link with Voldemort made it put me with you?" he asked, looking resolutely up at her.

"I never said you were linked, just that-" She paused, turning her head to consider him through slightly narrowed eyes. "You said link. Why did you say link?"

"No one told you?"

"Told me what?"

Harry looked at her for a moment, then, with a certain amount of hesitation, explained about the dreams he'd had over the past few years and about his scar hurting whenever Voldemort was having particularly strong emotions. When he had finished, Katherine was quiet, a thoughtful look on her face.

"You really didn't know?" he asked curiously; she seemed to practically be an expert on everything else.

"Was that why Severus taught you Occlumency? To keep Tom out of your head?" she asked slowly.

"How do you know about that?" asked Harry, face darkening in an instant. If she'd been consorting with Snape...

"Just something Bella said when I was posing as you," replied Katherine, appearing not to notice his changed countenance. "Said that Snape had told her you weren't very good at it."

"Why would she say that?"

"Because she tried to use Legilimens on me and I happen to be very good at it," said Katherine, a hint of a smirk tugging at her lips.

"What happened?"

"She got thrown across the room," replied Katherine, grinning at him. "So she probably won't be trying that one again in a hurry."

"I never did ask," he said quietly. "Why did you do that?"

"Take your place?" she asked, and he nodded. "Because Remus asked me to."

"Do you do everything he asks you?"

"Not everything."

"Most things?"

"Yes, most things." She half smiled to herself. "Most of the time."

He was about to ask what exactly she meant by this when the walls of the tunnel suddenly fell away and revealed a large chamber before them. Cautiously, they stepped out into it and Katherine flicked her wand at the orb that had lit their way so that it disappeared. One look ahead of them told him why.

"What is that?" he asked in an awed voice.

"Not entirely sure."

He exhaled slowly, looking up at the seething mass of white gold light that twisted up in front of them.

"Just how big d'you think this place is?"

Katherine tore her gaze away from the pillar of churning light and cast an eye around the chamber.

"About the size of St Paul's Cathedral? Bit bigger, maybe?"

"And all this is under London?"

"So it would appear. Might be under St Paul's, come to think of it."

"Or the Houses of Parliament?" he asked nonchalantly. Katherine glanced sideways at him, trying not to grin and failing.

"Or the Houses of Parliament," she agreed.

"Katherine!"

Katherine and Harry turned towards the voice and saw two figures in the distance, illuminated by the ethereal light.

"See, told you they weren't dead," she smiled, starting to walk towards them.

"I can't see Hermione," said Harry, frowning.

"No, but they were pulled in different directions, like I said," murmured Katherine thoughtfully. "I wonder..."

"What?"

"Well he used blood last time, didn't he? That's what you said? Blood to open the door?"

"Yes."

"So maybe he used it again this time – to split us up. The Avery's are as about as pure blooded as you can get and Weasleys are notorious for being blood traitors, so if they were together..."

"And we're both half bloods," Harry realised.

"Just about," agreed Katherine. "Not pure, anyway."

"But Hermione's muggleborn," said Harry suddenly. "She'd be left on her own."

"Looks like it."

"We have to find her!"

Katherine nodded as Ron and Robert reached them.

"Have you seen Hermione?" asked Ron, an anxious look on his face.

"No, but don't worry; we'll find her," answered Harry as Ron ran a hand frantically through his red hair. "What happened to you, anyway?" he added, casting an eye over his friend's dishevelled appearance; his clothes were torn and there were scratches covering his face and lower arms.

"Met a couple of Manes," muttered Robert, looking sagely at Katherine. "You don't look any the worse for wear, though."

"Nothing attacked us," replied Katherine, giving a one shouldered shrug. "Hurt my shoulder when I fell though."

Robert frowned and raised an eyebrow when she pulled her shirt across so they could see the swelling.

"It's not healing?" he asked in a concerned tone.

"It's not a direct blood injury," said Katherine. "Only cuts and poison heal quickly."

"Damn," sighed Robert. "You got a sling in that bag of yours?"

"Probably." Robert took the bag and rummaged through it till he found one, then helped her put it on.

"Where'd you think Hermione is?" asked Ron, watching Robert distractedly.

"There must be another entrance somewhere," replied Robert. "If we came through one, and you two came through another one-" he was cut off by the sound of screaming.

"Hermione!"

"No, wait!" Katherine yelled, but it was too late; Harry and Ron were already running across the cavern towards the source of the noise. Robert sighed, tying the sling firmly in place.

"Think you can run with one arm? Not going to be too unbalanced?" he asked, giving her a half amused look.

"I'm always unbalanced, Rob," she smiled back, turning to follow the boys. "I thought you knew that already." Robert grinned and ran after her, only slowing when he saw what had made Hermione scream.

"Inferi," he whispered, more out of shock than fear.

"Makes sense," replied Katherine, drawing her wand. "Nothing for me and Harry, because Tom's half blood and he doesn't want to be assaulted if he comes to check on his horcruxes, Manes for you, because at least you're pure blood, and Inferi for muggleborns, because they don't belong here."

"Do they know how much danger she's in?" Katherine looked sideways at him, a pensive expression on her face.

"From who?"

"That's not fair, Katherine."

"No? You didn't join for the social aspect, Rob," she replied softly as Harry turned his head to look at them.

"Fire's not working!"

"Maybe it's not hot enough," answered Katherine, catching sight of the brown haired girl at last; she was backed into a corner, Inferi advancing slowly.

"Do something," yelled Ron, trying to hex the nearest figures to no avail.

"Would fornax be strong enough, d'you think?" asked Robert, advancing on the assembly of living dead. "Katherine?" He glanced round and saw her standing where they'd stopped, not moving. "Katherine, what are you doing?"

Blue eyes flickered vaguely over to his face, and then she turned away, arms wrapped protectively around herself. Behind him, Hermione screamed again and he felt a hand tug at his arm. He looked around into Ron's desperate eyes and suddenly figured out what Katherine had noticed the first time she'd seen Harry's friends together.

Putting Katherine's odd behaviour out of his head for the moment, he shot a stream of white hot fire into the middle of the crowd, which shrank back instantly, flinching away from the heat and light. Ron ran forward and grabbed Hermione by the hand, pulling her towards the others, and Robert cast a quick shield charm to prevent the Inferi reaching them.

"Thanks," said Harry quietly by his side. Robert looked down at him, almost surprised.

"That's ok."

"What's up with her?" asked Ron softly, resting his chin gently on Hermione's head as she hung onto him, trembling slightly. Robert followed his gaze and saw Katherine hunched on the floor, head resting in her hands. He frowned, and called out to her but got no response. He sighed and walked over to her, crouching down before her on the ground and surveying her critically.

"What just happened there?" he asked, frowning slightly; she didn't usually freeze in the face of danger. "Katherine? Come on, say something, you're starting to scare me."

And then she raised her head and looked at him with eyes like black holes and suddenly he suddenly realised just how much trouble they were in.