Dangerous Obsession

Full summary: AU. It started as a mutual attraction that lead to an obsession. Lily Evans and Sirius Black were the perfect couple. James Potter and Sirius Black were closer than brothers. When a forbidden liaison begins between Lily and James they must hide their affair else it destroy the bonds of love and friendship that have taken a lifetime to forge.

Disclaimer: I don't own Harry Potter

Chapter One

"La da dum, back to school for me," Lily Evans absently hummed as she brushed out her long auburn hair. It was the morning of September the first, and Lily was getting ready to go back to Hogwarts School of Witchcraft and Wizardry for her final year. However, unlike every other year, this year she would be returning as Head Girl.

Lily finished brushing her hair and then scrutinized it in her mirror. Gah, I wish it would cooperate! Why does it have to be so... red! And big! Lily had always tried to make her hair do what she wanted, and, much to her annoyance, her hair seemed to delight in doing the exact opposite. Many people called it her crowning glory, but Lily didn't believe that for a second. "Look at it!" Lily would rant to anyone who would listen. "It's big and wavy. Wavy! Who wants wavy hair? Why can't it just be curly like I want it? You know, those ringlet-y curls?" Lily scowled, thinking about the speech she knew by heart, and all the poor people who had been forced to sit through it countless times.

After double-checking she had everything packed, Lily looked at her watch and cursed when she realized that it was past the time she had decided to leave by. She raced down to the kitchen at top speed to tell her parents it was time to go.

"Mom, Dad!" Lily called, tearing into the kitchen at breakneck speed. "It's time to go! I don't want to be late! I can't be late, I'm the Head Girl!" She stopped, hands on knees, gasping for breath. "Come on," she added exasperatedly as she saw her father leisurely eating some eggs and reading the morning paper.

Lily's father looked up from his paper, and then checked his watch. "Lily, we still have an hour before we have to get there, we'll make it in plenty of time," he said with a smile. "You're such a worrywart."

Lily stood up to her full 5'6" height, placing her hands on her hips and glaring at her father with all the energy she could muster. "I am not!" she said indignantly. "I just want to be the first one there. I'm Head Girl this year, and I should be there to greet the other students. So let's go!" Lily said, grabbing her father's arm as he chuckled, "Come on Dad," she whined, giving her best pouty face. "Please?"

Her father looked at her solemnly, but he couldn't hide the laughter in his eyes. "I don't know, Lil, there were a few things I wanted to do around the house before we leave. You don't mind if I mow the lawn first, do you?" he asked, watching in amusement as Lily began to get worked up

"I certainly do mind!" Lily said huffily, crossing her arms over her chest, annoyed, knowing her father was just pulling her leg, but unable to stop her reactions.

Lily's mother chose that moment to walk into the room, and chuckled at the sight before her. Her daughter was turning beet red and stomping her feet, and her husband was leaning back in his chair with a smile.

She walked over and placed a hand on Lily's shoulder. "Lily, you know your father is just joking," she said placatingly, "he just likes to rile you up."

"Yeah, I know," Lily said sheepishly, "he just knows how to push my buttons,"

Lily's mother smiled warmly down at the daughter whom she was going to miss so much. "So I gathered. Go grab your things, and we'll drive you to the station."

Lily leapt out of the chair she was sitting in. "Thanks Mom, I'll just be a sec," she said, beaming.

She hit the stairs running, taking them two at a time in her haste. She happily levitated her luggage, something she could do now that she was officially seventeen. As she bounced down the stairs, she thought about her last year at Hogwarts and what it would bring. Adventure? Maybe. Drama? Probably. Work? Most definitely. Lily had her work cut out for her this year. But she was up to the challenge.

She reached her parents' car and levitated her luggage into the trunk, as the car was in the garage, so no unsuspecting Muggles would witness this bit of magic.

Lily and her parents climbed into the car and took off, driving the familiar path that would take her to King's Cross Station for the last time. At this thought, Lily drifted into memory of years gone by, thinking about how much she would miss Hogwarts when she was gone.

"Hey Lil," her father said, looking at her in the rear view mirror, jolting her from her thoughts, "I know we already asked you this, but who's the Head Boy again?"

"Oh, um..." Lily paused for a second, thinking hard, "I'm pretty sure it's James Potter." Yeah, she remembered Sirius mentioning it in one of his owls earlier in the summer. She didn't know James well, they had only talked a few times, but being that he was Sirius' best friend, she knew a lot about him.

"And is he a nice boy?" her mother asked.

Lily smiled. Her parents were worried that this boy she would have to work with all year wouldn't be nice to her. Not to mention they were probably worried about her sharing living quarters with him. "Well, I don't really know him that well, but he seems nice. He is Sirius' best mate, and I trust his judgment."

Her mother's face brightened at Sirius' name. She always had liked him. "Oh, and how is Sirius? You two doing well? Wow, it's been nearly two years now, hasn't it?" her mother chattered.

"Yeah, about a year and a half," Lily said with a smile, thinking about her long-term boyfriend, Sirius Black. They had been dating since partway through their fifth year, and Lily had never been happier.

The rest of the ride passed in relative silence, with Lily remembering all her happiest memories with Sirius, all of which took place at Hogwarts.

Our first walk by the lake.

It had been just after her fifth year started, just as the sun went down. Lily had been ecstatic when Sirius had asked her to join him for a walk. They were the only two outside.

The first time we held hands.

That had been on another walk, two weeks after the first. Sirius had been so shy about it, but Lily had never felt the kind of connection she felt when Sirius had taken her hand with any other boy.

Our first date.

It had been a Hogsmeade trip, naturally, and Sirius had foregone all of his much-loved shops, like Zonko's and Quality Quidditch Supplies, in favour of going with Lily to her favourites.

Our first kiss.

They had been watching the sunset, and Sirius had said he had never seen anything as beautiful as Lily in the light of the setting sun, right before kissing her.

When he asked me to be his girlfriend.

He had set up a fancy picnic where he had told Lily he had never felt this way about another girl, and Lily had happily agreed to be his girlfriend.

Our first fight.

Lily smiled about it now, but at the time, she had been so upset. It was about something stupid, Lily couldn't even remember what anymore. Lily had started avoiding Sirius after the fight, but he had tracked her down in the library and gave her the most beautiful apology she had ever heard, telling her he was sorry and he never wanted to lose her. This was also the first time he told her he loved her.

Our first year anniversary.

Sirius had taken her out to dinner in a fancy restaurant in Hogsmeade during one of the Hogsmeade weekends, and they had a romantic dinner by candlelight.

Then there were all the small things he would do. He would bring her flowers for no reason. He was always able to cheer her up. He would come and bring her soup and her homework when she was sick, although he would have to get a girl to bring it up to her, as boys couldn't climb the staircase.

Lily was so deep in her reminiscing that it took her by complete surprise when they arrived at the station.

"We're here, Lily," her mother said, turning around in her seat and smiling at her daughter. Lily's head jerked up in surprise.

"Oh, already?" she asked, a bemused expression on her face as she got out of the car.

Her father ruffled her hair affectionately as he passed her on his way to the trunk. "You must have been in another world, kiddo. We were taking to you!"

"Oh, sorry," Lily said, her cheeks tingeing pink. "I was thinking." Her parents nodded as the three of them unloaded the luggage from the car.

Lily put all of her luggage onto a trolley and led her parents to the entrance of platform 9 3/4. Since they were both Muggles, they couldn't enter and had to say their goodbyes there.

Lily hugged her parents, promising to write frequently to them and assuring them that she would miss them just as much as they would miss her. She also promised them that she would say 'hello' to Sirius for them, laughing at this request.

"What's so funny?" her mother asked with a confused smile.

"Nothing," Lily replied. "I just never thought Dad would like any guy I brought home. It's just so weird that he actually likes Sirius."

Lily's father grinned. "I agree, it's unnatural," he said. "But the boy's too damn nice! It's impossible not to like him. Plus, he's polite, and he treats you well. Not to mention I can see how much he means to you."

Lily smiled before giving her parents a wave and running through the barrier into Platform 9 3/4. She had never gotten into the habit of casually walking through. Once through the seemingly solid wall, she stopped to take in the familiar chaos of the station thirty minutes before the train would pull out. She was most certainly not the first one there, as she had hoped she might be. The station was packed. There were kids everywhere, saying goodbye to their parents, meeting up with their friends, boarding the train. Lily absorbed the sight of the scared first years who didn't want to leave their parents, the cocky second years who were happy not to be those first years anymore, and so on, up to the confident and nostalgic seventh years who were preparing for their final trip.

Lily quickly scanned the crowds for her best friend, Jacqueline Dubois. She didn't see her, although she saw many other people she knew. Lily made her way to the train, saying 'hello' to everyone she recognized.

Eventually she managed to get onto the train and began scanning the compartments for Jacqueline. She found her about halfway down the train, reading a book. Knowing Jacqueline, it was likely to be a romance. As Lily slid the compartment door open, Jacqueline looked up. "Hey Lily, you look great!" she said, jumping up and hugging Lily.

Lily took her friend by the shoulders and gave her a good look. "Wow, Jacqueline, you look awesome! I love your hair like that! I can't believe you actually cut it!" Jacqueline was the same height as Lily and had light brown hair and hazel eyes. Before the summer her curly hair had been very long, but she had cut it so that it bounced just above her shoulders.

"Thanks. So how was your summer?" Jacqueline asked as she helped Lily to store her luggage away on the racks. The two girls sat down across from each other and began to catch up on what had happened over the break.

The girls talked until the train began to pull out, with frequent interruptions from friends and acquaintances they hadn't seen all summer, including the boy Jacqueline liked, Adrian Duclairc. He came in just as the train was picking up speed, and Lily made her excuses and left the two of them alone.

They're so gonna get together. It's so obvious, Lily thought as she began searching the compartments for Sirius. The sounds of loud laughter led her to the right compartment, where she pushed open the door and entered.

Sirius looked over at the door as it opened, and seeing whom it was, he leapt up. "Hey Lil!" he said, giving her a kiss. "It's been two whole weeks since I've seen you! How are you?" he asked, the two of them settling on one side of the compartment, his arm around her waist, across from Remus Lupin and Peter Pettigrew.

"Hi Remus, hi Peter. I'm good, and excited to be going back to school," Lily said in response to Sirius's question. "Oh, my parents said to say 'hi' to you. They love you, and I can't for the life of me figure out why!" Lily teased, kissing Sirius on the nose when he began to pout. "So what were you guys laughing about when I came in?" The boys looked at each other and grinned before launching into an elaborate, and surely exaggerated, story about some prank they had pulled over the summer.

"And then he said, 'but I don't like green!'" Sirius finished, leaving the four of them bent double with laughter, tears streaming down their faces.

By the time they calmed down, Lily realized that there was someone missing. "Hey, where's James?" she asked glancing around the room. Suddenly it hit her. "Oh no! He's in the Heads' compartment! Where I'm supposed to be! Holding a Prefects meeting!" Without another word Lily ran out of the compartment, leaving the three boys laughing at her forgetfulness. It was so unlike her.

Meanwhile, Lily had arrived at the Heads' compartment just as the Prefects were filing out. Once the last prefect had left, Lily shamefacedly made her way inside the compartment to see James immersed in a book.

"Hey James," she said meekly, toeing the floor. James looked up at her voice, and once he realized it was Lily, he closed his book and put it in his bag.

"Well, well, well. If it isn't Lily Evans, our current Head Girl," James said, checking his watch. "And she's only forty-five minutes late for the single most important meeting of the year. The meeting where we show the prefects who's boss. Where we show a united front. And, most importantly, where we show we are competent for this job!"

Lily looked horrorstruck by how badly James was taking this, and she felt as though she were about to cry. "James... I don't... I'm so sorry! I was with Sirius... lost track of time..." Lily sputtered, trying to explain herself, aghast at James' reaction. "It was an accident! I won't let it happen again!"

There was a beat of silence before James suddenly and unexpectedly smiled. "Lily, relax, I'm only joking. The meeting wasn't that important, and I handled it fine," he told her, smirking that his little joke had been so effective. "You should've seen your face! It was priceless! What till I tell Sirius!" James crowed triumphantly.

At hearing this, a wave of relief washed over Lily, and she sagged onto a seat as her legs gave out. Suddenly, what James did sank in and she glared at him. "James! I can't believe you did that! You had me so worried!" Lily slouched down in her seat across from him, crossed her arms over her chest and glared at him.

"Hey, you did miss the meeting, so I think you deserved that," James retorted, still grinning as he shifted so his back was against the wall and his legs were stretched across the seat. "I'm sorry, but it was really funny."

Lily reluctantly smiled back. "Yeah, I guess you're right...I am sorry, you know."

"I know. Let's just forget it," James said, making a motion with his hands as though brushing off what had happened. "Wanna know what you missed?"

As Lily nodded James began to fill her in on what had happened during the meeting: who the new prefects were, what questions they had asked, things of that nature. After they finished talking about the meeting, the conversation progressed to what they had done over the summer:

"Wow, you went to Romania?"

"Yeah, I have an aunt living there."

Then it moved onto their expectations for the coming year:

"It's going to be the hardest yet."

"Yeah, as Head Boy and Girl, we have a lot of work to do."

And finally to what they had in common: Sirius:

"Did he tell you about the time we..."

"Yeah, what about the time that..."

"And once he said..."

And before they knew it, they had arrived at the school.

"Wow," Lily said, looking out the window, "we're here already? Time just flew!"

James threw his robes over his shoulders as he said, "Yeah, well, I guess it's time to face the music." He offered his arm to Lily. "Ready Head Girl?"

Lily took the proffered arm with a smile. "I am if you are, Head Boy." The two left the compartment and proceeded to ensure that everything ran smoothly; all the first years went to the boats, and everyone else went to the carriages. Lily and James had to take the last carriage, as they had to make sure everyone was safely aboard before they left.

The ride to the castle was in relative silence as the two basked in the glow of being back at Hogwarts.

Once they reached the school, the two followed the crowd in, and once they got to the Gryffindor table, Lily followed James to where the Marauders were sitting.

"Hey Sirius!" Lily said, leaning down from her standing position to give him a kiss.

"Hey Lil," Sirius said, kissing her back. "What's up?"

"Just wanted to say 'hi' before I go and sit with Jacqueline."

"Ok, come and see me in the common room before you go to bed. You and James have new living quarters, right?"

"Oh, that's right!" Lily said, smiling at James. "Yeah, I'll come see you later. Bye!" she called over her shoulder as she went to sit in the spot Jacqueline had saved her.

"Oh, look!" Jacqueline exclaimed as Lily sat down, "there are the new first years! They're so small! And look how scared they are. I remember when that was us," Jacqueline added with a laugh. "It feels like just yesterday."

"Yeah," Lily agreed, looking nostalgically at the Sorting Hat as it was placed on the first child's head. "I can't believe it's almost over."

Jacqueline turned and grinned at her. "Don't worry about it, Lil. We still have a whole year ahead of us. Our most exciting one yet!" The girls settled into silence as the rest of the Sorting went on, cheering when new students were put into Gryffindor.

After the last student was Sorted, the feast began. Lily and Jacqueline happily ate as much as they could, chatting animatedly between mouthfuls, speculating about the coming year, who had changed the most over the summer, who had gotten together, and who had broken up. "Speaking of couples..." Lily said, looking sidelong at Jacqueline. "What's up with you and Adrian?"

Jacqueline blushed and looked down at her plate. "Well... I don't really know. I like him but... I don't know how he feels. I guess we'll just have to see how it goes." Jacqueline blinked and then laughed. "But I hope it works out!"

Lily smiled at her friend. "Don't worry. It's obvious he likes you too. Just give him some time." At this point, the feast had just ended, and Dumbledore stood up from his seat and gave the school the usual start-of-term announcements before allowing everyone to leave.

Jacqueline stood up and started to leave before realizing that Lily was not with her. "Hey, you coming?" she asked, turning around.

"Can't, remember? I have to go see Professor Dumbledore. James and I have our own rooms," Lily reminded her friend.

"Oh, that's right!" Jacqueline said, smacking her forehead with the heel of her hand. "Hey, I want to see it! How about you show me tomorrow?" At Lily's nod, Jacqueline began to walk away. "See you tomorrow. Good luck with the new rooms!"

Lily waved goodbye to her friend before making her way over to James, who was waiting for her. "Hey James," she said, smiling at him. "Ready to see our rooms?"

James grinned at her as they walked over to Dumbledore. "Of course! It's gonna be great having my own room! You should hear the noise in the boys' dorm, what with Peter and Sirius snoring. It's lucky I ever get any sleep!"

Lily snorted at this. "I bet! That's not a problem I usually encounter in the girls dorms, but I am looking forward to getting my own room."

Just then the pair reached Dumbledore, who was standing by the front doors. "If you two will follow me, I'll show you where you will be staying," Dumbledore said, his eyes twinkling as they so often did. "How were your summers?" he asked conversationally as they walked. They spent the rest of the way chatting lightly about this and that, until they reached a painting that depicted a field of flowers with a little girl nestled amongst the long grass, playing 'he loves me, he loves me not' with a daisy.

"Password?" she asked in a girly voice.

"I've taken the liberty of choosing a password for you," Dumbledore said, looking at Lily and James. "It's 'Draco Dormiens Nunquam Titillandus. As you know, that is the Hogwarts motto, and it means 'Never tickle a sleeping dragon'. Make sure you remember it, as it is the only way into your rooms. Also," Dumbledore said, looking pointedly at James, "do not tell anybody else this password. It is meant for you two alone. Good," he said as the two nodded their heads in acquiescence. "Then I will leave you to your rooms. Good night," he said, turning and walking away before Lily or James could say anything.

The two looked at each other for a moment before Lily said, "Alright, let's go in, then," before turning to the little girl and saying, "Draco Dormiens Nunquam Titillandus."

The portrait opened and James stood back to allow Lily to go through first. Once James had gone through, he stood beside Lily and observed the room. It was about a quarter of the size of the Gryffindor Common room and painted a deep blue. There were two comfy looking armchairs and a couch with a coffee table in front of it, all grouped around a stone fireplace. There was a half-full bookcase with room enough for any books Lily and James had, which stood against a wall beside a desk that was twice as long as a normal desk, with two chairs placed in front of it and two sets of drawers down the side. There was also a big bay window with a cushioned window seat in it, which overlooked the Quidditch Pitch.

"Wow," Lily said, her mouth hanging open. "This is awesome! Who knew there were such great perks of being Head students?"

James laughed a bit as he walked over to the desk, pulling open the drawers and looking inside. "Blank parchment, that's it. Yeah, this is pretty great. Wait till Sirius sees it! He'll never leave!"

Lily's face lit up as Sirius' name was mentioned, and she stopped her examination of the books already in the bookcase. "Yeah, he'll like it. His own private place to hang out in," Lily said before catching herself. "Well, at least, he'll think it's his own private place. We'll have to tell him otherwise, or else we'll never get rid of him!"

Lily and James both laughed at this as they walked up the single staircase before splitting up to check out their bedrooms once they reached the top. Right at the top of the staircase was the bathroom, to the left was Lily's room, and to the right was James's. Lily walked into hers, which was painted a deep, forest green, her favourite colour. There was a nice four-poster with a cream comforter, a dresser, a night table, a wardrobe, and a vanity table. All of it was done in a cherry wood. Lily walked to the window where she peered at her view of the Great Lake for a minute, before turning and looking at her room again, nodding as she found she quite liked it.

Lily turned as she heard her name. "Lily!" she heard again, obviously coming from James. "Come check out the bathroom!" he called out. Lily walked over to the other door in her room, figuring that it lead to an adjoining bathroom. She was right. She walked in to see James already in there, put some of his personal items away. The bathroom was painted a cheery yellow and was very large. The stand up shower took up a large part of one corner, its frosted glass winking in the brightness of the overhead light. The bathtub was large, square, and inground with about five or six taps with different bubble baths. The sink and bathtub were marble, and the sink had space for toothbrushes and other personal necessities.

James' door was open, and Lily quickly peeked in. It was a deep burgundy, and was otherwise the same as Lily's, minus the vanity table. He instead had a mirror over his dresser.

"Well," James said from behind Lily. "I think we hit it lucky! This is fantastic!" Lily turned to see him trying the different taps.

"Hm...vanilla," Lily said, sniffing the air as James turned on the second tap. "My favourite. I doubt we hit it 'lucky'. I'm pretty sure the rooms are the same every year. Well, except for the colours."

James and Lily both turned and left the bathroom through a third door that lead into the hall between James and Lily's rooms at the top of the stairs. "You're probable right. Hey, I'm gonna head to Gryffindor and see the guys. You wanna come?" James asked, walking over to the portrait hole.

"Sure," Lily replied. "I promised Sirius I'd come." Lily and James left their dorm and went to the Gryffindor common room, making small talk along the way. Once they had climbed through the portrait hole, Lily looked around the room to see if Jacqueline was in there, but she was nowhere to be seen. Probably with Adrian, Lily thought to herself as she headed for Sirius. She looked over her shoulder and saw James heading towards his other friends.

Sirius tried to split his time up fairly between Lily and his friends, generally eating his meals with the guys and hanging out with them half of the time. They got Friday night, Lily got Saturday night. It also helped that Lily also had Jacqueline to hang out with.

Lily hung out with Sirius for a couple hours, just talking and cuddling on a couch by the fire. Once it reached about 11:30, Lily checked her watch and realized she ought to head off to bed.

"Sirius, I've gotta go," Lily said, giving Sirius one last kiss.

"Are you sure?" Sirius asked, grabbing her by the waist and pulling her onto his lap, where he kissed her.

"Yes, I'm sure!" Lily said, giggling. "It's time for me to go to bed! We have class tomorrow." Sirius groaned at this remark.

"I know but-" he was interrupted as Lily kissed him.

"Alright, night Sirius. I love you," Lily told him as she stood up.

Sirius stood up as well. "I love you too, Lil." Sirius pulled her into a hug before pushing her gently towards the entrance. "Night."

Lily looked around to see if James was still there, and spotted him in a corner with Remus and Peter. She made her way over to them. "Hey James, I just wanted to let you know I'm heading out. It's getting late, and I need my beauty sleep," Lily told him with a smile.

"Alright," James said, looking up from his heated chess match with Remus and returning Lily's smile. "I'm gonna stay here for a bit, but I'll be up soon," he promised.

Lily said her goodnights to the other boys and then turned and left the common room, looking over her shoulder just as she was climbing out to see Sirius still looking at her. She gave him a smile and a wave just before the portrait closed.

Lily walked back to the Heads' rooms. She yawned as she walked up the stairs to her room, just realizing quite how tired she was. She got ready for bed before climbing in and turning out the lights. Her new bed was very comfortable. She was asleep within seconds of her head hitting the pillow, slipping off into a world of dreams of the year to come.