Author's Note: Hello, all! :) Welcome to my fanfiction. Go ahead, pull up a chair (though, odds are, you're already sitting in one), pour yourself a goblet of butterbeer, and settle in. Just a few things before we get started. First off, here's a more in-depth summary, below:

Before she was Narcissa Malfoy, she was Narcissa Black: soft-spoken, silly, caring toward others, and best friends with her cousin Sirius.

But then came Lucius Malfoy: brave, strong-willed, and determined to get what he wanted at all costs.

Despite every instinct in her body telling her to run the other way, Narcissa is drawn to Lucius by an attraction that cannot be shaken. He might be dangerous, even poisonous to her beliefs, but love doesn't like to listen to reason...

Second, often when I write a fanfiction, I have a cast list in my head. With the main characters when reading the actual HP books, I create the character with my imagination. Even when writing fanfics centered around the Trio, I use my own imagination of what they look like. But when writing a fanfiction on lesser-known characters, I like to use a certain 'cast list' to be more inspired with relationship-developments and such.

Anyway, my particular "casting" for this fanfic is: Narcissa Black - Dianna Agron; Lucius Malfoy - Alex Pettyfer; Sirius Black - Jonathan Groff; and Bellatrix Black - Katie McGrath. Of course, your imagination may not at all agree with who these characters look like, but these are just the people who I used.

Alright, I feel like I've been babbling a bit much, but all of these things I felt I needed to tell you. One more thing: This story is slightly AU: Narcissa, Lucius, Sirius (and all of his friends) are all in Seventh Year together. I understand that this is not how the ages actually corresponded in the books, but for my story, this is how it needed to be. Consequentially, Bellatrix is actually younger than Narcissa, though I know she is the older sister in canon. Sorry, but again, that's how it needed to be for my particular story.

Disclaimer: I do not own anything from Harry Potter except for this plotline. Also, this story is not endorsed by or affiliated with any of the actors whom I used with my "casting."

And now I give you the first chapter of my fanfiction This Poison Called Love. I really hope you enjoy it, and reviews are always encouraged! XD


"I'm just telling you, there's no way Slytherin is going to beat Gryffindor if they make it to the next round of the Quidditch matches," Sirius Black was saying to his cousin Narcissa Black.

Narcissa gave him a mischievous smile. "We'll see about that. I've been watching my fellow Slytherins practice, and they've got a few tricks up their sleeves."

Sirius grinned. "Oh, come off it! Stop acting like you know anything about Quidditch."

Narcissa pretended to look offended. "Excuse me, but just because I'm a girl doesn't mean I'm ignorant to the world of high-flying sports." She pressed her hand over her heart. "I resent your stereotype."

"Noted and ignored," Sirius said. He slung an arm over Narcissa's shoulders. Rolling her eyes at his antics but grinning, Narcissa leaned into his side and rested her head against his.

They were strolling down the hallway, headed to Potions class. Though Narcissa was a Slytherin and Sirius was a Gryffindor, their Houses shared Potions together.

They reached the staircase leading down to the dungeons. Sirius slipped his arm off Narcissa's shoulders and executed a comically formal bow, sweeping his arm toward the stairs.

"After you, milady," he said.

Narcissa stuck her hands on her hips and shook her head defiantly back and forth. "Nuh-uh," she said. "Didn't we just have this whole women-are-as-capable-as-men conversation at lunch?"

Sirius straightened up and shot Narcissa a look that was half-amused and half-exasperated. "How is me letting you walk down the staircase first an insult to your gender? I'm just being a gentleman!"

Narcissa smirked. "Never thought I'd hear those words leave you lips with you keeping a straight face."

Sirius cracked a grin. "You know what? If you don't want to go down the stairs first, then I will."

"Good," said Narcissa, fighting back a grin. She loved their silly banter.

As Sirius was beginning to walk down the stairs, Narcissa quickly hurried after him, cutting off his path. "Race you to the classroom!" she shouted.

"Hey! That's not fair!" Sirius protested. "You caught me by surprise, you ruddy cheater!"

Giggling like mad, Narcissa bolted down the stone staircase, skipping every other step. She could hear Sirius' quick footsteps behind her, his breathing ragged with laughter. She'd reached the bottom step and was about to deposit herself onto the ground when Sirius' hand reached out and seized her elbow.

He used her as a catapult, swinging himself forward and gently pushing her aside. She stumbled off the step and hit the ground, landing on her hip. It smarted a bit, but other than that, she was completely unharmed.

Still, if Sirius could play dirty, so could she.

"OWW!" she cried out, contorting her face into a mask of pain. She gripped her ankle and rocked back and forth. "My ankle!"

She heard Sirius' footsteps abruptly stop and then start again as he changed course and dashed back over to her.

"Oh no, are you okay?" he asked, bending down and gingerly touching her ankle.

"I think I sprained it when you pushed me aside," she said, trying to inject her tone with whimpering. She was a pretty good actress, if she did say so herself.

Sirius wrapped one of his arms around her waist and pulled one of her arms over his shoulders. He hoisted her to her feet, helping her stand so she wasn't putting any pressure on her 'sprained' ankle.

"Do you need to go to the nurse?" he inquired, sounding very concerned. Narcissa finally opened her eyes, knowing that now that she did so, the jig was up.

Sure enough, Sirius noticed the amusement and slyness glowing in her eyes. Her lips soon followed, carving out a playful smirk.

She only had a second to watch his expression go from worry to surprise to mock-outrage before she ducked away from him and began sprinting down the hall. Laughter rang freely from her. She heard Sirius yell something incoherent that sounded vaguely like a curse word.

She reached the end of the hallway and stopped, doubled-over with guffaws. She was laughing so hard that it was impossible to continue running.

Sirius caught up with her shortly after. "You little monster!" he yelled, though he was laughing, too. He very lightly slugged her on the arm. "Hope that bruises," he said.

"Like I bruised your ego?" Narcissa smirked.

"Enough with your cocksure attitude, 'Cissa," said Sirius. "I'm going to have to teach you a lesson." He rubbed his hands together menacingly.

"A lesson in how to be a loser?" Narcissa teased. "You're surely an expert at that."

"Your hair looks nice today," said Sirius, advancing even closer to her. "Very straight and smooth."

Narcissa's eyes widened. "Oh no!" she gasped. "Not the hair!"

Sirius nodded slowly, his entire face one big smirk as he pinned her head against his shoulder with one hand and used his other fist to rub against her scalp: the classic noogie.

"No, no, no!" she cried, squealing with laughter.

"Yes, yes, yes!" Sirius corrected. "Who's the loser now?"

"You still are!"

"Admit that I rule and you drool, and I'll let you go."

"Okay: I rule, you drool. Now let me go!"

Sirius laughed so loudly that it sounded like a bark. "Nice try, but you know that's not what I meant."

"I shall never admit defeat!" Narcissa declared, struggling to get away from Sirius' noogie.

"Then your hair will pay for it," Sirius said, grinning down at the static mess of pale blonde strands atop his cousin's head.

Finally, Narcissa tickled Sirius under the armpits, just then remembering it was his weak spot. He squealed like a girl and quickly released her. They both clutched their sides, howling with guffaws. After a few moments, their laughter subsided into chuckles and they regained their composure.

"Alright, time to head down to Potions," said Sirius. "Wonder what Slughorn's got planned for us today."

"Hopefully it's a potion that'll reduce hair frizz," Narcissa said, only half-joking. She used her fingertips to quickly comb out the tangles on her scalp; after several strokes, her hair was back to normal.

She and Sirius turned the corner and started toward the Potions classroom. The scene unfolding outside the classroom door made them exchange a furious look and hurry over.

"Give it back! Please, Lucius, I have to get to class!" begged Roger Milborn, a fellow Seventh Year who was unfortunately short for his age (about five-foot-two). He was jumping up and down, trying desperately to get back his Potions essay, which none other than that weasel Lucius Malfoy was holding high out of his reach.

Seeing as how Lucius had at least a foot on Roger, it was hardly fair. And the teasing was not at all in good fun.

Lucius stared down at Roger with cold amusement shining in his eyes. A devious smirk stretched across his lips. His cronies laughed in their stupid, har-har-har way.

"Well, since you asked so nicely," Lucius hedged, pretending to think it over. "…NO!"

Roger was starting to panic; thin beads of perspiration sprouted along his forehead. He really needed to get his Potions essay back, but there wasn't much he could do about it. If he tried to stand up to Lucius or told on him, Lucius would curse him into next week.

"Hey, marshmallow-brain," Sirius growled, stepping beside Roger and fixing Lucius with a heated glare comprised of the deepest loathing. "Give him back his essay, before I have to make you do so."

At five-foot-eleven, Sirius was a few inches shorter than Lucius' looming stature, but the fierce look in his eyes and the malice of his tone made up for the height difference.

Narcissa stepped around Roger, coming up on his other side so that he was protected from both ends. She drew her wand and glowered at Lucius and his cronies. She would let Sirius do the talking but would have his and Roger's back if the fight progressed into more than just words.

Lucius' smirk dropped off his face, replaced with a look of dark hatred. Even though the look was aimed completely at Sirius, Narcissa felt a terrible chill dance down her spine. Lucius Malfoy, despite his Third Year-level antics of bullying, was not someone to be messed with.

Lucius' cronies cracked their knuckles, glowering at Sirius. Narcissa felt invisible, and she didn't know if she was grateful or resentful of that fact.

"And what do you propose you're going to do about it?" Lucius asked Sirius, his upper lip curling in disgust.

Sirius pulled his wand out of his robe pocket; Lucius did the same, still keeping Roger's essay high out of reach with his other hand.

Narcissa wasn't going to let a fight break out. She was no expert at arithmancy, but simple counting told her they were outnumbered five to three (and that was even if Roger decided to fight back – the odds might turn out to be five to two).

She pointed her wand at the parchment gripped in Lucius' hand, focused all of her concentration on it, and muttered clearly under her breath: "Accio Roger's essay."

It worked like a charm (no pun intended) – Roger's essay zoomed out of Lucius' fist, and only magic could account for it not being ripped in half as it did so. It landed gracefully in Narcissa's outstretched palm, and she promptly handed it over to Roger, whose eyes shone with gratitude and admiration toward her.

Lucius yelped in pain; his palm had been split by a nasty paper cut. He dropped his wand as he clutched his injured hand with his other hand; driblets of scarlet blood trickled down his palm and splashed to the stone floor.

Lucius turned his glower to Narcissa. But, unexpectedly, his narrowed eyes softened as they met hers, and he quickly focused his furious attention back on Sirius. Lucius began to bend over to collect his wand, but Sirius' foot had already landed on top of it, keeping it caged from Lucius' lunging fingers.

"Stupefy," one of Lucius' cronies – a hulking lad with a mean face by the unfortunate name of Elmer – bellowed, shooting his curse at Narcissa.

She was so busy watching Lucius and Sirius that she didn't see it coming; the next thing she knew, a jet of red light was zooming toward her in her peripheral vision, and then she felt the force of the spell knock into her chest like a fist, and then she hit the floor, unconscious.

The last thing she heard was an outraged cuss word yelled at Elmer that sounded strangely like it came from Lucius Malfoy.