Author's note: This is my first fic set in the Marauders' era so I would be grateful for any feedback or comments you could give! I have the bulk of several chapters already written but I would be happy to take on board any suggestions you have for improvement. Just so you know I'll be sticking to canon as much as possible, but I am not going to give away the final pairing until near the end.

This initially started off as a parallel story to A Trickery with a Twist to give some depth and background to Snape's reactions, but it's morphed into a piece that easily stands well alone. I hope you enjoy this as much as I'm enjoying writing it!

The Great Mistake of Severus Snape

After calling her a Mudblood, Severus struggles with his intensifying desire for Lily Evans. But his fight to regain her friendship and earn her love is hindered not only by James, who takes up Dumbledore's special defence class with Lily, but also by himself. Can he succeed as the tension heightens between Lily and her two admirers? Or will Severus' mistakes spiral out of control?

Chapter 1. A drop of luck

Severus was practically hopping outside the dungeons by the time Professor Slughorn appeared at the doorway to let the sixth years in for their first NEWT lesson. Having arrived a full ten minutes early with the hope of catching Lily beforehand, Severus had once again been forced to suffer her poignant absence and sink back into his miserable reflections over his own wretched situation.

All summer long he had yearned for the chance to speak to Lily and apologise for his hurtful behaviour after the OWL exams at the end of last year. He had wished for all he was worth that he could admit he had been wrong and rid the horrible picture of her face contorted in hurt and betrayal from his mind. But in all their weeks at home, when they were so tantalisingly close to each other, Lily had refused point-blank to see him and he had been denied any chance to plead his guilt and win her back as his best friend.

So he had counted down the slow torturous weeks, waiting with mounting anticipation for yesterday, the First of September, when they had taken the Hogwarts Express… only to find that Lily had chosen a seat in a compartment with Potter and his gang, and there was no chance Severus could express his mind in their company.

And all since then Lily had been streaking around the castle from one place to another as if the wind was behind her and he was entirely invisible to her. Even in Charms that morning she had not once looked at him – Severus knew, he had been unable to resist twisting round to glance at her every few seconds - at least until Potter had noticed and subsequently teased him that he had ants in his pants… Severus grimaced at the memory. The four Gryffindors' howls of laughter had attracted Professor Flitwick's attention and since he had not been concentrating on his charm and could not perform it, he had been delayed from leaving on the bell. So he had had to patiently wait there, itching to catch up with Lily while he was laboriously given extra homework and took what was rightfully Potter's scolding… and was once again denied the chance to make his apology to Lily. He recalled how swiftly she had exited the classroom.

It then occurred to him that Lily was acting as if she very much wanted to avoid him… A frown settled on Severus' face as he leant back against the cool, hard stone wall and balled his hands into tight fists. This was unbearable…

Knowing she was here, in this very same castle, about to be in the very same room, made Severus beside himself with a potent mixture of highly-strung nerves and excitement. His heart was jolting about inside his chest as if he had all the energy in the world, but the rest of his body felt so weary from all the nervous adrenaline that had been overpowering his blood for the last few days that he didn't know what in the name of Merlin to do with himself; he paced backwards and forwards in front of the door; he stood still; he went and sat on the steps; he leapt up and fidgeted on the spot; he tried leaning against the wall again… and by the time it was two minutes until the lesson was due to commence and other students began arriving, swiping from him his chance for confronting Lily in private, Severus thought he might just explode with the impossibility of the situation.

As soon as the door was open he rushed past a baffled Professor Slughorn into the cool dungeon and set up feverishly at his usual table, feeling immediately at home laying out his various books and ingredients in his favourite classroom. A devious smile formed over his lips – he and Lily always worked together in Potions so this time he was sure to be granted with her company. He felt the most cheerful he had for some time as he arranged the roots and herbs on the table in the precise order he knew that Lily liked them to be in. It felt good to know that soon she would join him and he would lift the suffocating weight off his chest.

After a minute spent with bated breath, Lily entered the classroom.

Severus lifted his head hopefully, striving to catch her eye. But with horror he saw that Lily did not even glance over to him. Lily lifted her chin and marched pointedly in the opposite direction, taking up seat with Remus Lupin instead.

Severus' jaw dropped open in hurt and betrayal. He knew he had offended Lily, but he had not expected this show of spite. He found himself still gaping when Peter Pettigrew bobbed into view. He also seemed to find this change of situation incomprehensible and was revolving in the aisle like a spinning-top, unsure of where to go or what to do. Finally his shoulders dropped despondently and he wound his way over to Severus' table, snatching up the only free stool and scooting to the furthest inch of the table as possible. A growl of annoyance escaped Severus' mouth and provoked a squeak from Pettigrew, who promptly toppled off his stool and was forced to grapple with the table to stay upright.

Great, Severus thought angrily, slamming his knife down onto the table so hard that Pettigrew flinched and he made a dent in the wood, Lily hates me and now I am lumbered with this idiot. As Slughorn called everyone to attention, his eyes moved sullenly over to Lily, who was seemingly in deep conversation with Remus. But as if she felt Severus' burning gaze upon her, her eyes flicked suggestively to meet his. She saw the ferocity of the emotions in his intense stare and she dropped her gaze, blushing. Severus' eyes narrowed as he analysed the frown forming on her face. Was this a little sign that she was ashamed of her cruel behaviour? Or was she scolding herself for even just looking at him? Severus sighed, answerless, and his eyes turned to mere slits.

Lily was now looking very distracted. She seemed to be struggling to give Remus an adequate answer but at that moment James Potter leaned over from the adjacent table and saved her the embarrassment. Severus saw with repulsion that his eyes were bright, clearly triumphant that Lily had finally discarded her Slytherin friend and joined the other Gryffindors. He said something that caught Lily's attention and she turned instead to listen to him, removing her face from Severus' scrutiny.

Severus glared at James murderously, hating him for stealing Lily away. He refused to listen to a word Slughorn was saying and was trusting that his Potions instincts would get him through this class with the winning potion as usual. He couldn't help but resign to the conviction that it would now be incomprehensibly difficult to get Lily to accept his apology - if he could even offer it to her at all with her shunning him like this. For a while Severus took out this vicious frustration by imagining what it would be like to force a poison down Potter's throat and watch him squirm and writhe at his feet; but then James' eyes shot from Lily to him and a smug little smile ignited on his face, forcing Severus to look away scowling bitterly.

He was then distracted from his dangerously morbid thoughts when he saw Lily's hand rise into the air. As her voice filled the echoic dungeon Severus cottoned on that she was answering a question from Professor Slughorn.

"…I think it's Felix Felicis, sir."

At the sound of her voice an involuntary sigh eased itself out of Severus' parched lips, momentarily anaesthetising his pain. Slughorn's words slowly filtered through his drugged consciousness.

"…Indeed that is right, Lily! And this is the prize I am offering at the end of this class for the pair who can brew the best Draught of Living Death. For those of you who do not know, this is a prize well worth striving for – but no students have yet brewed me a perfect draught. Nevertheless, turn to page ten of your new textbooks and we'll see how rusty your potion-making has become over the summer. Off you go, and good luck!"

Now Severus was sitting bolt upright, no longer festering in a foul mood, his thoughts running quickly. Felix Felicis, he knew what that was. It was liquid luck, and if he needed any luck, it was now… He knew that it would take far more than luck to get Lily to change her mind about him, but if she was hesitating – if she felt something for him – a little drop of luck might be all he needed to push her over the edge…

Severus smirked, feverishly fingering the correct page of his textbook. A couple of feet away, Pettigrew copied him and fumbled with the pages of his book, too. Severus nearly felt like laughing when he scanned the list of ingredients for the potion. Only two days into his summer holiday he had taken his tattered copy of their book for sixth year potions out of his trunk, and with the aim of impressing Lily he had proceeded to practise as many potions as he could during his time at home and even toy with improving them. And the Draught of Living Death… Aha! This was easy. The only problem was… Pettigrew.

"Do exactly what I say," Severus snarled at Pettigrew, who quivered as if he had just been slapped, and Severus immediately set to chopping up his Valerian roots with refined haste. "Crush these beans with the side of my knife."

There was an odd stifled sound and Severus spared the podgy boy next to him a withering look; he seemed to be struggling between the urge to say something and his fear of being snapped at.

"What?" he demanded.

Pettigrew's eyes flicked across the classroom to where his friends were, clearly further away than he found comfortable. "It says here we should cut up the beans…" he mumbled, fumbling timidly with the knife.

"If you want that Felix Felicis, you will have to crush them!" Severus said dismissively, sprinkling the first few ingredients into their shared cauldron.

Pettigrew gave another squeak and promptly dropped the knife, narrowly missing his own foot. Severus rolled his eyes. At this rate, Pettigrew would only be crushing Sopophorous Beans this lesson, but perhaps that was a good thing. Severus admired his purple potion and then cast an inquisitive glance over to the Gryffindors. To his pleasure, James was bickering with Sirius and Lily looked quite stressed as Remus stirred their potion feverishly. For a second, Severus was overcome by the sorely tempting impulse to go and reveal to her his secret of the beans… but then he remembered the Felix Felicis and a cunning smile tweaked at his lips. No, if she wouldn't work with him, he would beat her to the prize and earn her respect that way… he would make her regret her choice to abandon him.

When Slughorn called time up Severus was trembling with undiluted excitement. Having avoided having his little finger chopped off by Pettigrew and elbowed him out of the way just in time to stop a disastrous addition to their concoction, everything had gone smoothly. He had checked and double-checked his little notes in the margins, but for the most part he remembered his improvements to the recipe, having last made this potion only a few weeks ago. He was sure the contents of his cauldron were perfect.

Slughorn began perusing the class, tentatively peering over the rim of each table's cauldron and sniffing the curling vapours. Severus watched him intently and noticed with anxiety his expression change from impassiveness to eagerness as he looked into Lily and Remus' cauldron. Before he knew what he was doing, Severus had a lapse of faith in his own ability; he slipped out his wand and muttered, "Confundus!"

"Hmm…" Slughorn smiled pleasantly but moved on from Remus and Lily without further comment. Lily's hopeful expression fell and Severus smiled smugly, the tension easing from his muscles. Any moment now…

"Oh my!" Slughorn exclaimed. "Oh my, oh my! The clear winner! What a perfect lilac colour, just as if I had brewed it myself. Here you are, Severus. Well done, as always." While he fumbled around in his pocket to find the vial of Felix Felicis, Slughorn looked to Severus' side to also praise his partner. However, upon seeing Peter Pettigrew, not Lily Evans, he merely gave a weak smile before whole-heartedly shaking Severus' hands and bestowing upon him the golden vial. Severus grinned voraciously and looked at James, who quickly turned away, his shoulders sagging with disappointment. Severus licked his lips and, checking that nobody else was paying him any further attention, unstoppered the vial and took a brief swig.

Beside him Pettigrew gaped, but Severus chose to ignore him and packed up his things, finding an uncharacteristic feeling spreading throughout his body and mind. All of a sudden he was feeling as happy and encouraged as if he was already halfway there in persuading Lily to reconsider him. He had to restrain the urge to skip out of the classroom and then he bounded up the stairs, seconds later catching up with Lily and Remus.

"Lily, could I have a word?" he said, uncharacteristically brightly. She and Remus both turned hesitantly as if surprised at Severus' audacity to confront her. Lily looked like she wanted to give an excuse but before she could come up with one Remus smiled amicably at Severus and carried on up the stairs, joining James and Sirius and abandoning Lily on her own. She lowered her eyes to her feet, clearly unhappy at being deserted with Severus, and stubbornly refused to even meet his unmoving gaze.

"You should come back to our table next class," Severus suggested, keeping his voice soft in an attempt to ease her into conversation.

Lily remained scowling and watched the rest of the class file by. "Why would I want to do that?" she said acidly. "Our draught was just as good as yours. I don't need your help in Potions."

Her words were sharp but the hopefulness Felix had brought on refused to be stung by them. "But you need your friend," Severus said softly as they were left alone on the stairs. "I know how lonely you were over the holiday, with no one but your muggle-sister for company… Admit it, you missed me Lily."

"Have you been spying on me?" she demanded accusingly, flicking her eyes angrily onto him and then away once more. "I thought I made it quite clear that first week of the holiday when you waylaid me in the park, I didn't want anything more to do with you. James is right, you can be creepy."

Severus sighed, feeling hurt that Lily was professing to be as repulsed by him as he had always feared. He even avoided slating off James in an attempt to persuade her he wasn't the twisted dark creature she seemed to believe he now was.

"I just wanted to check you were okay…" he pleaded. "I thought you might be feeling down after what happened at the end of last term…" He was thinking of the breaking of their friendship.

Lily glared at him. "You mean when you called me a Mudblood?"

"Oh." Severus quickly gathered his thoughts, startled by the intensity of her gaze. "Yeah, Lily, I'm sorry. I really am."

She looked at him scathingly. That apology had been rather lame after all, he realised.

"No, wait! Lily, please listen, I honestly am sorry!" He held her beautiful green eyes unwaveringly. "I really am so sorry for calling you that name. It's been haunting me all summer long and it's been torture not even having the opportunity to apologise to you properly. I wish you could forgive me…" He wondered how he could live without those emerald eyes ever settling upon him again.

Lily's lips were pursed in a thin, tight line, which for the first time made Severus think of her sister Petunia. She was analysing him sceptically. "If you were really sorry Severus, you would tell me why," she decided eventually.

He winced. "Lily, I never meant to hurt you! I was just scared and angry, and so humiliated that I panicked and the word slipped out! But I regretted it instantly–"

"You refused to apologise!" she cut in.

"Well, almost instantly," Severus corrected himself. "But after the whole summer… I've barely been able to think of anything else… I am so ashamed of what I did, and I have been so afraid of losing you, Lily… You're not a friend like any other… You mean everything to me, surely you must realise that…?" His voice dropped to a haunting whisper.

Lily was staring at him, her eyes round and searching.

"Lily? What is it?" he whispered. Severus now realised that he had revealed a little more of his feelings for her than he had planned. Fear suddenly seared through him. It was so unlike him for his tongue to be loose and betray the emotions he carefully concealed deep within… perhaps it was Felix taking control of his words.

"I-" Lily stuttered, seemingly stunned. Still staring she swallowed. "I thought you would say you were sorry that you've been hanging out with the wrong people and that you felt remorse for all your dabbling in the Dark Arts! Not…" she trailed off and blushed.

"Oh…" Severus watched the rosy colour spread over her cheeks and smiled seductively. He liked seeing Lily behave this way his presence. "Well?" he finally said softly. "Will you accept my apology?"

Lily glanced up and he looked directly at her, striving to read her thoughts. There was something fragile shifting in her eyes but he couldn't quite read it. "Okay, Severus," she murmured finally, putting great weight on each word. "But this is your very last chance."

However nothing could dampen the aching happiness that was radiating throughout Severus' body now.

"I won't disappoint you," he said swiftly and sent her a meaningful glance. Lily smiled shyly and glanced away. They began to walk together up the stairs towards the Great Hall for dinner, Severus trying very hard not to spring up the steps three at a time and leap for joy.

"I was really disappointed not to win the Felix Felicis you know," Lily admitted as they climbed together. "I'm kind of used to being the best in the class, when I'm with you." She granted him a little smile. "And actual luck…" her voice trailed off wistfully.

Deep in thought, Severus looked at her… He had won her back, and that was what he had prayed for, wasn't it? He had got everything he wanted. He didn't need the Felix Felicis any longer.

"Here, take it." He came to a standstill at the top of the stairs and held out the vial, three-quarters full.

"What?!" Lily looked at him as if he was mad. "I can't take it, Sev!" Ah, she had used his nickname; she was not cross with him any more! "Slughorn chose you; you deserve it."

An uneasy trickle of guilt slid down Severus' spine. Who knew who would have won it, had he not had a lapse of faith and confounded their teacher? Perhaps Lily should have won it – she was incredibly skilled at potion-making after all.

"I want you to have it. You deserve it, Lily. I promise. It's the least I can do."

He stretched out his hand, the gold leaping at his fingertips. Lily slowly opened out her palm and Severus pressed the vial onto it, savouring the heavenly touch of her soft fingers brushing his.

He looked up into her eyes and she smiled, all suspicion and coldness gone. Instantly Severus felt that he had done what was right to get Lily back on his side by trusting his instincts.

After a dumbfounded silence, where Lily checked she was actually holding the vial of Felix Felicis once more, she spoke breathlessly. "Wow… Thank you so much, Sev!"

She stowed the bottle carefully into the depths of her robes and Severus smiled. At that point over her shoulder he saw James walking towards them across the Entrance Hall, seemingly having left his friends at dinner. Normally Severus would have felt full of hatred and, if he confessed it, threatened by this rival's approach in his constant crusade to prise Lily away from him, but today he felt merely amusement at the Chaser's attempt to blight his reconciliation with Lily.

Lily followed his gaze and turned to acknowledge James. "What is it?" she asked. But James' eyes were fixed on Severus only.

"Aren't you going to give Peter his fair share of the liquid luck?" he addressed Severus, frowning.

Severus sniggered. "I did."

"That's mean," said Lily quietly.

"No!" Severus hastily explained, "All he did was try to cut off my fingers with my own knife! I brewed the entire potion, no thanks to him. He doesn't deserve any of it."

"Nor do you, bullying my friend like that," said James defensively. "I don't wonder why he tried to cut your fingers off. He deserves the liquid luck even for that!"

Severus menacingly took a step closer to James and James whipped out his wand. Instantly Severus did the same. Just as the heated atmosphere was about to boil over, Lily stepped between them and forcefully separated them.

"Look, it doesn't matter!" she said. Both boys instantly flagged at her contact and willingly let her push them away from each other, as if eager to do anything so long as she touched them. "James, Sev gave me the Felix Felicis. You don't need to be so bitter that he beat you."

James looked like a little puppy that had been hurt. "I'm not bitter, I'm glad you've got the potion!" he said keenly, his eyes pleading her to understand. Lily ignored this and instead flashed Severus an appraising smile that made him swell with pride.

"But I don't know why you're both so friendly again, you hated each other at the end of last year!" James whined.

"Sev has apologised," Lily said neatly.

James gave him a once-over and then gaped at Lily in disbelief. "What – and you accepted? After all he's done? After what he's still doing? Are you mad? What made you do that?"

Lily pouted. "Thank you, James, for giving your views on the state of my mental health. But Sev has been very kind. Would he have given me this if he was as horrid as you imagine?" She held up the little vial containing the coveted golden liquid. "Come on, Sev, let's go to dinner."

Severus smirked, elated that Lily had praised him in front of James. He made to follow Lily across the Entrance Hall, but then he saw the look on James' face. His eyes were moving rapidly from the vial Lily was currently stowing back in her pocket, to Severus, and back again.

"You had some!" James breathed, gazing at Lily's retreating figure. Severus stopped and raised his eyebrows. Finally as Lily disappeared into the Great Hall without them, James dragged his eyes back to Severus, filled with animosity. "You tricked her!" he accused.

"No I didn't, Potter," Severus hissed. "It's not against the law to take liquid luck, only in competitions and examinations. So don't accuse me of doing anything wrong."

"But you did drink some, didn't you?" James pressed heatedly. "That vial's not full anymore." When Severus chose to stay silent, simply smiling craftily, James nearly exploded he was so incensed. Severus laughed.

"You won't get away with this, Snivellus!" James snarled. "Lily's too clever to be duped by your trickery."

"You're talking rubbish again, Potter," Severus replied airily, casually heading towards the light and delicious smells spilling out of the Great Hall. His eyes picked out Lily, whose face was filled with delight as she showed a gleam of gold to one of the girls she shared a dormitory with. Severus smirked.

"Wait!" Severus looked down to see James' restraining hand on his arm.

"What now?" Severus growled, annoyed. James pulled him roughly back into the shadow behind the doorway.

Severus looked up to see that James was looking him squarely in the eyes, a hard look on his face. "Don't you dare look at her like that."

Severus cocked an eyebrow. "What are you on about?"

James was unfazed. "You know what I mean. Don't look at Lily so… greedily. It's sickening. She's not simply a possession you can win like the liquid luck. She's much more than that. She deserves someone far better than you."

Severus blinked. "You shouldn't look at Lily as if you want to grovel at her feet and worship her. That's sickening. There's nothing more pathetic than that. Besides, you're no more than a desperate, brainless show-off, and Lily knows it. So quit acting like a prat, Potter."

And with that last sharp quip, Severus slid free of James' slackened grip and sauntered into the Great Hall, nearly singing for the joy of his extraordinary ordinary day. From now on, it seemed to him, things could only get better with Lily.

xXxXx

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