I don't own Harry Potter.

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Equal and Opposite

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Only Sirius and Bellatrix were still fighting. They didn't seem to have noticed the arrival of Dumbledore. Sirius ducked the red light that shot from Bellatrix's wand. He laughed and egged her on.

"Come on, surely you can do better than that!"

A second jet of red light hit Sirius on the chest. He only had time to adopt a surprised expression before he gracefully sank through the veil…

--

Prologue

--

Harry woke up with a start, his breath ragged, body slick with sweat. The unmistakable coppery taste of blood reached his bleary brain, his tongue throbbing sharply in his mouth. Grimacing, he looked over to his clock.

Three in the morning.

Head clearing slightly, he hung his legs off the side of the bed and walked over to the shared bathroom. Sidling up to the counter, he looked in the mirror and saw a worn and tired looking Harry Potter stare back at him.

Madam Pomfrey refused to give him more Dreamless Sleep potion, nor did Voldemort cease his relentless attacks on his mind, flooding his unconscious mind with the scent of death, the pain of pillaged homes, and the screams of burning mudbloods.

And when Harry thought he could finally sleep through the sight of tortured children falling under the onslaught of Death Eaters, the Dark Lord dredged up images of his murdered Godfather, simulating it again and again through his mind until he woke up, resolving to never sleep again.

Studying Occulumency turned out to be fruitless. Although he found himself with some skill in the art, the fundamental bond between them made any such deception easily overcome in his sleep.

Grabbing some extra clothes, he took a quick shower, relishing the cleansing spray against his body. He dressed and made his way to the common room, invisibility cloak and Marauder's Map in hand. This had become a nightly ritual for Harry lately. Whenever he couldn't sleep, he explored the massive castle that was Hogwarts.

He had quickly noticed that the map charted nowhere near the entire castle. Much of the ancient fortress was unused, abandoned and forgotten. Filthy hallways plunged in darkness held testaments to the past, sinister portraits lining the walls. Grimy floors were covered in a blanket of dust.

Harry had discovered many classrooms that hadn't seen humans in centuries, textbooks detailing forgotten, or, as Harry had quickly come to learn, illegal magic. The instruction of the Dark Arts had once been a part of Hogwarts, part of its shunned history. All that was left were the blocked off, boarded up rooms and hallways of years past.

--

Stepping out of the portrait, he looked for any signs of his minder, activating the Marauder's Map and looking for the metamorphmagus the Order had assigned to him.

Tonks had been given the task of keeping an eye on him, mostly likely to make sure he didn't repeat his performance at the Department of Mysteries fiasco. Taking the form of an exchange student, she always lurked in the background, watching him.

Thankfully, she was still unaware of his activities of late and was blissfully asleep in the girl's dormitories.

Clearing the map, he made his way to the third floor. The third floor was the largest of all the floors, but it had for the most part been abandoned. It held little in the way of classrooms, instead serving as storage. Placed half-hazardly in the halls were statues of fearsome vampires, dragons, and other such dark creatures. In a storeroom he had even come upon a life-sized sculpture of a dementor. He shuddered. The stone piece of art also replicated the vile creature's aura, albeit at a weaker level.

So it was with good reason Dumbledore had hidden the stone on this floor – it was dark, dusty, mostly unlit, and had enough twists and turns to rival the maze in the third task. One could easily get lost in the pitch black that dominated most of the area.

Ascending the stairway leading to the third floor, he stopped halfway and brought up his wristwatch.

3:13.

Leaning against the rail, he started tapping his feet impatiently, waiting. Seconds stretched to years as he stood there, gazing at the infinite blackness above. Annoyed, he spared another look at his timepiece.

3:14.

The stairway groaned as it moved, rotating itself until it connected with the shadowy Eastern Wing of the third floor. He had discovered this particular secret of the castle accidentally, witnessing it springing to life before his very eyes. The stairway was thought to never move, and was thus one of Neville's favorites. The mere fact that it moved at one precise moment implied something.

So, he had taken to discovering its secrets at every chance. The time that it chose to move was an amusing tribute to muggle mathematics – no doubt implemented by Rowena Ravenclaw herself.

Leaping quickly onto the landing, he watched as the stairway moved back to its original position. This had caused Harry to panic the first time he had come, thinking he was trapped there until the next day. Wandering through the unknown the entire night, he had found himself back on the second floor hours later after numerous twists and turns that had him hopelessly lost. Tracing his steps back, he had come to a solid wall. Apparently it was only a one-way path.

Torches were nonexistent here, so he was forced to light his wand.

"Lumos!"

A thin beam of light burst out of his wandtip, dispelling the black shroud that cloaked the area.

Stepping forward, he started at a brisk pace, scanning his surroundings nervously. He had only been here a few times, and was still cautious. Many dangerous creatures thrived in the darkness, and this was the perfect place to live.

Not that anyone would miss him, of course. After Ron and Hermione had admitted their feelings for each other, Harry had become an irritation to them, a third wheel. They smiled at him, sure, and they still walked and studied together from time to time, but it wasn't the same. They had eyes only for each other and would gaze at him as if they held some kind of secret he wasn't privy to, almost pityingly.

But it went beyond pity.

Even with the barrier separating them, they still managed to question him casually on a day to day basis, as if nothing was wrong. Talk to him about his life, how he was feeling. It was with false cheer that they did so, empty and utterly meaningless, out of place in their usual behavior.

Almost forced.

Recognizing this, he had looked beyond the Golden Trio, searching for companionship with others.

He had failed, miserably.

Harry had realized that he truly did not have any friends besides Ron and Hermione. Growing up as he did, he clung on to the first two he got his hands on, and neglected to make more friends less Ron and Hermione get offended.

To Hogwarts, even though he had been there close to six years, he was still a distant figure to most. Even though he had instructed the D.A., he hadn't really bonded with anyone, shying behind his role as a teacher. Trying to converse with others, he had received odd looks of disbelief, their eyes flickering over to the other two thirds of the famed threesome.

It was then he had realized that he was truly alone.

--

Passing a portrait of a manticore slaughtering a village, Harry stopped. He hadn't seen this before…

The painting stood near the entrance of a passage. Stepping in, he was struck with a sense of age. The air hung heavy here, and he could feel the slight tingle of magic. Warily, he took a step ahead, wand at the ready.

Rough, bare granite walls extended forward several feet, but came to an abrupt end. No, it couldn't be pointless. Everything in the Castle had a purpose, held some secret. Studying the dull grey wall that ended the passageway, he discovered a faint outline. Moving closer, he traced the rectangular crack in the coarse rock with his hand. He blinked. It was a door.

A door? To where?

Curiosity overtook caution as he tried pushing on it without success. Casting a silencing charm on the entire corridor, he hit the rock in front of him with several unlocking charms without avail.

Furrowing his eyebrows, he contemplated the mysterious door. Had he not studied the wall up close, he would have passed off the cracks as natural. But they were too perfectly cut to be natural. What could possibly be behind it?

He decided to look around for clues. Perhaps the door had a hidden switch? He scanned the walls on his sides, looking for anything unusual.

There was nothing.

Turning around, frustrated, he noticed a slight shimmer at the edge of his vision. Stepping closer, he watched as the light bent slightly around the area. It was impossible to see unless you were looking for it. Focusing his eyes a bit, another portrait appeared, flickering into existence.

Shining his wand on it, he observed the newly revealed painting.

A snake, lion, badger, and an eagle guarded what seemed to be weapons, dark artifacts, and various treasures from a group of gathering students. He watched in fascination as a figure in black stepped away from the crowd and pushed in a hidden square block in the wall in front of the guards. The animals vanished and the students raided the treasures.

A smile graced his lips. It was ingenious. Looking back at the wall, he looked for a square block. He found it moments later. It seemed like it was only possible to see the block after viewing it in the painting. Reaching toward it, he pushed it in.

At first, nothing happened. But then a long groan sounded as he was rewarded with the door sliding back, revealing a pitch-black corridor.

Stepping forward, he brought his wand up to examine the place. It was a very narrow opening, as narrow as the door. The rock above him was low, a few inches above his head. Looking behind him one last time, he plunged in.

--

Musky, moist air filled his lungs as he walked forward, every step kicking dust up in the air, visible in the wandlight. After a tense ten minutes of walking in complete silence, he reached a stairway. Quickly making his way downwards, he came upon a round antechamber.

The air here had cleared noticeably, lacking the oppressive quality the passageway above had. The stones were still moist, however, and the ground was just as damp.

The rock above formed a small dome, supported by several pillars placed in the edges of the room. Drops of water fell to the cold stone, the sound amplified by the structure of the antechamber.

He was under the lake.

Drawing his robes tighter, he looked around. There were nine hallways leading out of the antechamber, the entrances elaborate arches between the pillars. Each was identical to the others, including the one he had entered through. Seeing this, Harry took off his cloak and placed it at the entrance lest he get lost, the rainbow shimmering of the invisibility cloak being highly visible.

Bringing his wand up, he peered down the length of the nine hallways. Nearly all of them led downwards. The ninth however, ended a short distance away with a door. Not in the mood to walk anymore, he headed down the last one.

He came upon a heavy wooden door. It was completely blank with the exception of a carving near the top. Focusing the shaft of light on it, he studied the seemingly random marks on the wood. There were dots connected by lines. It looked like a constellation. Searching his mind, he recognized it.

The constellation of Gemini.

Unable to control his curiosity any longer, he pushed the door open and entered.

Stepping into the pitch-blackness, he looked around cautiously, checking for any danger. The stupidity of his whole situation hit him at that moment. He was walking into an unknown, dark area that was guarded against to ensure the student's safety. Alone.

Perhaps Snape was right, he was arrogant and brash.

But he wasn't about to leave now, go back to sleep, back the screams, the pain, the death and carnage.... Taking a deep breath, he summoned all his famed Gryffindor courage and took a step ahead.

Reinforcing his light with yet another whispered 'lumos', he continued, wand lighting the darkness around him in a circle of dull-grey, paved stone. He moved shakily forward, checking his surroundings until he felt the darkness lighten up ahead. Continuing at an increased pace, he noticed small candles that began to line to walls on either side of him. Extinguishing his light, he walked on.

Suddenly, he stepped out of the corridor into a small chamber, half the size of a classroom. It was lit by a few weakly flickering candles.

But there was one glimmer that penetrated the darkness in the damp room, an unnatural shard of light that caught his attention. He took a sharp breath as he recognized the object at the back of the room. The ornate gold feet, the tall, lustrous gold frame - and of course, the glass. The luminous glass reflected nothing at the moment, its surface a rippling silver mass.

"Erised," he whispered.

The mirror gleamed, as if in response.

He stood there for a few moments, in disbelief. But he felt a deep longing, an almost carnal need to see what Erised would show him now. He stepped forward, wondering what he would see now, five years after his initial encounter. His parents. Or, perhaps, Sirius. Yes, definitely Sirius…

But as Harry stepped forward, his heart pounding in his chest, he saw –

Nothing.

Emerald eyes stared back at him, reflecting his confusion, disbelief. Remembering what Dumbledore had said, he was sure that he was not the happiest man in the world.

So why was it showing him without any desires? He ran his hand through his hair in frustration. He watched as his reflection did the same. Heart still pounding, he took a closer look at the mirror, studying its frame, the glass, its back. As he walked back to the front of it, he realized something. The words around the frame weren't the same.

Immediately his wand was in his hand, clenched tightly in his fist.

This wasn't the Mirror of Erised.

--

Moving toward the mirror carefully, he traced his hand along the words around the frame.

Erised had the inscription 'Erised stra ehru oyt ube cafru oyt on wohsi'. In reverse, it read 'I show not your face but you hearts desire.'

This mirror, however, read 'Etisoppo dna lauqe esoht tub dlrow ro ecaf ruoy ton woshi'

Harry reversed the words in his head.

"I show not your face or world but those equal and opposite," he read, voice soft. Equal and Opposite? He walked back in front of the mirror and froze.

Where the mirror reflected him before stood a girl. A rather beautiful one at that. He stood there gaping. The girl had long black hair, creamy white skin, and emerald eyes. Even stranger was the fact that the girl was not mimicking his actions. In fact, she was standing there, her arms folded, an amused look on her face. On her forehead was…the scar. The same lighting bolt scar that marked his forehead was also present on the girl's, albeit much lighter and nearly invisible. Oddly enough, it seemed to add to her beauty, rather than detract from it.

'Equal and Opposite…?

The girl stepped forward, placing her hands on the mirror, her emerald eyes gleaming with eagerness. Eyes so much like his own, yet different. They were as green as his, but were nowhere near as hesitant.

Harry unconsciously stepped forward, putting his hands on the glass, covering the girl's.

The glass gave off a soft ripple. He felt the glass grow warm under his palms, becoming softer. Looking back up at the girl, he saw a curious expression on her face, one that was suddenly replaced by determination. Her hands came alive, locking into his. The glass rippled around her fingers, sending off little waves. He felt himself pull her from the mirror. The girl came through and looked at her surroundings. Letting his hands go, she stepped up to him and gave him a searching gaze.

--

Harry stared back in shock, unable to think.

The girl gave a soft melodious chuckle that broke Harry from his stupor. He tightened his hand on his wand, stepping back. Harry saw a deep hunger in her eyes, like a huntress gazing at her prey.

"Who…who are you?" Harry managed, face one of suspicion. His scar was giving off a curious buzz, albeit a pleasant one…

The girl gave him one of his own lop sided grins before answering.

"I…am you."

Harry blinked. Him? Sure, she looked like a bit like him, she even had the trademark scar, but he was male. The figure in front of him clearly was not.

She seemed to pick up on this. Giving him a disturbing predatory smile, she stepped forward, eyes shining in anticipation.

"I am you, your equal and opposite," she whispered. As she placed her hand on his cheek, he stiffened. She ignored him and started caressing the side of his face.

"So beautiful…" she murmured, eyes raking over his face and body, startling Harry. He blushed deeply. He'd never thought of himself as…well, anything. He was never one to comment on beauty, let alone himself.

She smiled at his blush. She looked up, emerald eyes meeting perfect replicas. Harry felt distinctly uncomfortable as they searched him, seemingly reaching into his soul, uncovering his every secret. Her hot breath brushed over his face, causing him to shiver. Noticing this, she smirked and brought her other hand up, holding his face in both hands. She leaned in, whispering into his ear.

"So sad, so defeated…what have they done to what's mine?" she breathed. Harry shivered again at her use of the possessive. She pulled away and started walking around him, hands brushing over his body. She took his arm, and brought it up to her face. Pulling the sleeve back, she traced the scar made by the basilisk with a single finger slowly, taking in all the details. The contact was sending tingles throughout his body and his heartbeat quickened. Cocking her head, she dropped it and put her arms on Harry's chest.

Leaning forward, she put her ear against his heart and closed her eyes. Harry felt the warmth of the body pressed up against him, so familiar, yet so different. It was…comfortable in a way he couldn't put his finger on. Harry's other self had apparently noticed too, as she pressed herself tighter against his body. She had closed her eyes, basking in the warmth provided by him. They both stood there pressed against each other, breaths synchronized, hearts beating simultaneously.

--

Harry felt a haze come over his mind. He felt lost in the warm feeling that enveloped his mind and body. He welcomed it, letting it wash over him. But something like fear started to wind through the haze, penetrating his mind. Something like whats happening who what where when why - and Harry pulled away, not suddenly, but gradually, his mind and body slowed by the thick fog that blanketed his senses.

The girl, his other self, looked up at Harry, looking slightly put out at losing Harry's proximity. Her face changed into the familiar hunger, the animalistic desire he had seen before. But something new filled her eyes, something that made Harry more than a little nervous.

Lust.

She moved forward again, pushing Harry into the wall with almost supernatural strength. Harry was too startled to do anything to retaliate, so he looked on as she placed her hands on his waist, slipping them under his shirt, warm digits dancing across his chest. Harry melted into her ministrations with a slight moan. It should have been impossible that her simple touch could have affected him so much…

She leaned in again, this time nibbling at the bottom of his ear before moving onto his neck. She could feel his heart rate increasing, his breath irregular. She stopped slowly, almost lazily and looked into the eyes of her counterpart, taking in the sigh that he gave when she had reached the nape of his neck.

"Beautiful," his counterpart murmured again and she pressed up against him once more. She moved her lips over his gently, softly brushing back and forth, back and forth until Harry was dizzy.

He felt the haze taking over his senses once again, enveloping him in a warm blanket. It was like a missing toy long gone that had been returned. He felt complete, more than complete, content. But the fear returned, once again worming through the dull barrier that surrounded his mind. He broke off the kiss, looking at the flushed face of his other.

"Wha…what are you doing?" he managed, his breath ragged. Why was his voice so husky?

She gave him a mysterious smile, and replied in her captivating musical voice.

"Why, I'm kissing you of course," she said matter-of-factly. She pressed herself against Harry once more, her pelvis grinding into his. He felt himself responding to her touch.

Somehow, he couldn't bring himself to care anymore.

Her face lit up at his response, and she attacked his lips with a new fervor.

She placed a hand on his scar and traced it back and forth. The normally painful mark was extremely sensitive, and the touch from his other sent tingles of pleasure throughout his body. He moaned again in her lips, before breaking off once more.

Withdrawing, he found himself on top of his other, sprawled on the ground. She stared back at him, pupils dilated, her breath ragged. Harry was suddenly turned over, finding himself on the bottom. His counterpart captured his mouth in another fierce kiss, sending his mind back into the haze.

She pressed herself against him tightly, enveloping both of them in the beckoning warmth. Her lips still locked into his, she moved her hands through his messy hair, massaging his scalp and rubbing behind his ears. Harry closed his eyes against the sensations.

She was on him again in an instant, mouth hard and hot on his, his hands fumbling with her clothing. Harry was borne back to the ground by her slight weight; she laughed breathlessly and pulled at his hair, yanking his face up and plunging her tongue into his mouth. The excitement shivered along his skin, and Harry felt himself pulling her closer, hands pulling at her back, pressing her mounds against his chest as she lay on top of him. She groaned into her mouth, grinding against him.

Then he was in her, hard and hot and pulsing inside her, deep ragged thrusts on the edge of pain. Emerald eyes locked into each other as she slid against him, her hands on either side of his head, dark black hair a curtain around his face. The sensation was incredible, trickling down from his scar and tearing through his body. Soon his other was shuddering against him, skin flushed. She pressed her lips against his mouth, bucking weakly as pleasure ripped through them, tipping them into oblivion.

--

Harry awoke hours later, something warm in his arms. He was sitting against the wall, with his other straddling his waist, arms and legs wrapped around him. Her head was nestled deep into his neck, hair falling over his chest. Their damp, bare bodies were covered in a hastily conjured rough blanket.

He sighed in contentment, numb in the warm haze. It was more intense however, unlike before. It wasn't the towering highs of an orgasm, nor was it the electrifying pleasure of the Dark Arts. It was like being smothered in a blanket of euphoria, belonging, and freedom. Tightening his hold on his counterpart, his other, his self, he fell back into peaceful slumber.

--

When he opened his eyes again, he felt empty, but oddly at peace. She was gone. Looking back at the mirror, he caught the flowing of a cloak and billowing ebony hair before it disappeared behind a tall wooden door.

Getting up, he picked up his wand, moving to the neat stack of clothes on his left. On top of it sat a short note written in elegant writing, opposite of his own. Reading it, he smiled.

Putting on his clothes, he took one last look at the mirror before he left, shutting the door behind him.

--

Harry stumbled into the Common Room just as Ron and Seamus had finished a game of Exploding Snap. Taking one look at his flushed face, Ron chuckled.

"Well, you had a good night. Who was it?" he asked, amused. Harry's eyes got a far off look and he gave a small smile.

"Someone who understands," he replied. And with that, he went into the dorm for a few more hours of sleep. Ron and Seamus looked at each other puzzled.

Because in the end, only Harry Potter could ever understand Harry Potter.

A/N: Edited to make the sex scene less juvenile and take out the 'I-miss-Sirius' bawling.