Chapter One

A/N: This is a five parter; each chapter will be rather short. But if you're looking for a fluffy HEA that is predictably cheesy, then you've come to the right place. Thank you to karelia for the beta. You're the best and give the greatest gifts of commas ever. :P ~Meladara~

Professor Hermione Granger's Arithmancy puzzle is the stuff of legend at Hogwarts School of Witchcraft and Wizardry. Well, recent legend, at least. As the resident Arithmancy professor for the last five years, Professor Granger allows all her students the opportunity to decode the huge equation that encircles the entire perimeter of her classroom, and though many have tried, none have succeeded. Such is the a complexity of the computation, it has even been rumoured that several master-level Arithmancy colleagues of the professor made an effort to solve it but failed. And this is exactly how Professor Granger wants things.

~oOOOo~

Originally, the puzzle had been an incentive to get her students involved and keep them engaged in her class. It was her first year of teaching, and as an inexperienced teacher, she was having a particularly difficult time keeping her seventh-year students engaged. It was a desperate attempt, she knew, but unable to come up with another tool to motivate them and frustrated beyond belief at her students' inability to focus, she promised them that over the spring holiday she would encode a secret into an Arithmantic riddle. The first to solve the puzzle would win a prize. However, when the professor had made this promise, she had failed to consider the potential for trouble in doing so.

Over that spring break holiday five years ago, Hermione Granger had thought long and hard on which secret to include in the algorithm for the puzzle. What should it be? She had many secrets, belonging both to her and to others. Knowing that she could not impart upon her students a secret belonging to another, she had to face the reality that it would have to be a secret of her own. Furthermore, as she began the project, she quickly discovered that in her frantic and earnest attempt to engage her students, she had magically bound herself into including a tried-and-true deep secret. Something so powerful that no other person knew. Immediately, she had known what knowledge she would have to impart; there was only one secret that was strong enough to satisfy the magic of her promise.

Aghast at this realisation, Professor Granger finally decided that if she had to share her secret with the world, then the least she could do was protect it in the most complex magical equation ever created. Carefully, she had worked late into the nights that holiday, magically encoding her secret. Into the equation she also built in a series of fail-safes that ensured just before anyone solved the riddle, she would be notified and they would be bound to silence on the topic. Of course, the professor justified the use of the master-level secrecy clause under the premise that it would spoil it for others if the secret were told, but truly, she knew better.

As far as the prize, she decided that any student capable of solving the equation would be rewarded with a letter of recommendation and a dinner in Hogsmeade with a friend耀upervised, of course; the first person who solved it would also receive 100 galleons.

~oOOOo~

For five years now the puzzle has sat unsolved. Professor Granger lives in relative contentment that the security surrounding her secret is sufficient, and although it does sometimes prickle her nerves that her secret is there for anyone to find, she sleeps at night with relative ease.

However, there is one major factor that Professor Granger has not considered, and that is Professor Severus Snape. Hermione Granger is aware, of course, that Professor Snape is a brilliant man who is extremely knowledgeable in many subjects. Indeed, she even knows that he is a rather good Arithmancer, but she never counted on him having any active interest in solving her puzzle. After all, he has never paid her any mind otherwise; why should he care about the puzzle encircling her classroom?

~oOOOo~

When Professor Severus Snape had first heard of her puzzle and reward, he'd scoffed. It was a rookie move and would not truly encourage the students to learn in the long term. No doubt, he'd thought initially, it was a purposefully easy problem applied to the situation in order to falsely boost self-esteem and morale among her bored students. However, as the years passed and the stories of Professor Granger's Arithmancy puzzle grew, Professor Snape, against all odds, found himself intrigued.

Then, this summer, Professor Granger had invited two Arithmancy colleagues round for a few days, and they too had tried to solve her riddle洋uch to her chagrin, he had noted. But they failed just as all others before them. Indeed, he'd overheard them talking about it as they had dined.

'The utter beauty and complexity of such a problem,' one had raved. Then they had gone on to hypothesize that the magical calculation had somehow taken on the characteristics of the encoded secret itself and, indeed, was so magically complex that it was solvable only by the creator and perhaps only a few others in the entire world.

After that he knew that he had to see it.

There was simply something utterly enticing about an unsolvable puzzle. It was a true challenge, and Severus Snape loved a challenge. Surely he would be able to work through it. He knew he wasn't technically an Arithmancy master, but he was exceptionally skilled in the subject and certainly better than any seventh-year in this school.

And that is exactly how Severus Snape had found his way to her abandoned classroom one afternoon just days before the new school year was to begin.

~oOOOo~

He entered the room and immediately began to study the writing that encircled her room. It was stunning and clearly the most complicated piece of Arithmancy he'd ever seen. It was clear why this was the fifth year the puzzle would be unsolved. Truly, he doubted that this year there would be anyone smart enough among the student body to crack even the first few sequences. Amazed at the intricate beauty of the problem, he thought, If Arithmancy is an art, then this equation is a masterpiece.

After an hour of painstakingly copying it all, he quickly ran a spell of his own devising to make sure that he'd made no mistakes, and then he returned to his dungeon chambers, thankful that Professor Granger had continued her yearly tradition of leaving the castle to visit her dunderheaded friends in the days before the start of the school year. As he settled in for the evening with a brandy close at hand, he began his work, intent on solving her puzzle, if at all possible, before the start of the new school year.