The Room of Requirement is an odd room. No matter how many different things Neville asked for, he found them there. A room to hide in? Done, complete with a bed and a toy toad. A room to study in? Who could forget the DADA's training setup.
But Neville had expected a lot more out of it today. He'd been miserable, unable to get more of a reaction out of Ginny Weasley than "that's nice, Neville" when he'd brought her the beautiful blood-lily he'd been tending especially for her birthday. And so he'd found himself walking up and down a certain corridor, muttering to himself "I need a room that holds the secret to how to make everything good come to me."
Three passes, and he saw a door appear. A little door. A door barely large enough for a milk bottle. Neville opened the door, and found a little bookcase, wide enough and tall enough for only one book. Which sat in the space, waiting for Neville to pull it out. Which he did.
Its cover was brown, like a scroll that had been at the back of the library for too long. On the front was a seal, or rather, a picture of a seal. It seemed fairly unremarkable, except for the title.
The Secret.
Neville gasped, and opened it immediately.
"As above, so below. As within, so without."
He flipped on a few pages.
"We all work with one infinite power. We all guide ourselves by exactly the same laws..."
Fascinated, Neville wandered off to his bed, nose stuck in the book. He devoured it, finished it as the moon started gleaming into the window of his dormitory, then started it again, ending up falling asleep over it not long before the Saturday morning sun crept into the room.
...
When finally he awoke, Neville knew just what to do. Throwing on some clothes, he raced back to the corridor where the Room lay, and walked quickly backwards and forwards three times, muttering "A room to change myself in. A room to make me someone Ginny will notice - tough and strong and able to stand up to those damned Carrows".
The door appeared. Neville tentatively pushed it open, and then gasped. There, in front of him, was a gym. A fully-set-up gym with mats and weights machines and elliptical trainers - and a cupboard full of shorts and singlets so he could get sweaty, and beside it, a full-length mirror. Taped beside the mirror was a training schedule, nicely laminated and arranged by activity, and with a pen to fill in the boxes with his targets...
"Oh my." Neville walked around the room, stroking the handlebars of the elliptical, hefting a large medicine ball (then quickly putting it down and picking up a much smaller one). He was almost at the end of the room when he spotted the weighing machine. Looking around nervously (although there was no-one else in the room with him), he stepped onto the machine.
"NINE STONE EIGHT, OR SIXTY-ONE KILOGRAMS, YOU PUNY WEAKLING. START ON THE WEIGHTS NOW. USE THE BLUE ONES AND LET'S SEE YOU DO IT."
Neville jumped off the machine in fright. How in Merlin's name? Then he noticed - in the mirror was ... him! But dressed in shorts and a skimpy net top, and hefting up a pair of weights. And scowling at him!
He walked over to his "reflection" and peered at it.
"You want me to do this?"
The reflection nodded, and gestured towards the cupboard with clothes, and then the weights.
"Well, ok, but you'll have to help."
If it was possible for a silent reflection to say "well, dur!", the image of other-Neville in the mirror would have done it.
...
An hour later, anyone passing the tapestry of Barnaby the Barmy would have seen Neville staggering out of a normally-nonexistent door, barely able to walk. He'd had a shower and changed back into his school robes, but was so exhausted that he'd put his sweater on inside-out, and his hair was wet. His face was also as red as a tomato, and he stumbled a little as he headed down to the Gryffindor dormitory for an early night.
As he lay on his bed though, he whispered to himself "Twice a day. And three times on weekends. If I keep thinking I'll make it, I'll make it. I'll show her..."
...
Other students at Hogwarts didn't notice the change. Winter robes hid the slowly-building muscles, and while Neville's puppy-fat finally disappeared, most assumed it was the effects of stress and the constant terror campaign by the New Administration of Hogwarts. Slowly, surely, Neville increased the time of his training, following the silent advice of his avatar and the encouragement in The Secret. To inspire him, the mirror also showed crowds of other students doing the exercises with him, or short inspirational films. His weight changed little in the first few weeks, but his body-shape was shifting into something approximating his avatar, and he started leaving off the shirt while he worked out so he could admire the slowly-appearing six-pack.
...
It was nearing the Easter Break, and life under the Carrows had become unbearable, when Neville finally had the chance to make his move. He had snuck out late at night with Ginny and Seamus and a large pot of paint, and they were busy painting "Dumbledore's Army" in large red-and-gold letters across the wall of the dining hall, when Mrs Norris came prowling past. None of the trio noticed her prowling through the doorway, nor did they spot her turning tail and racing out to notify Filch. For a squib, the caretaker was good at moving silently, and the first indication they had was when Neville and Seamus found themselves being turned by a pincer-like grip on their ears.
"Desecrating the hall, are we? Putting up graffiti, are we? I'll have a chance to use those shackles in my office this time, I'm thinking!"
Neville reacted without thinking, using both his forearms to ram Filch's arm. The blow knocked the caretaker's grip off, and Neville dropped to his knees and then tackled Filch in a move that would have made his mirror-image very proud of him.
"You'll not take my friends!" the lad yelled as he threw the caretaker to the ground. The attack surprised Filch so much that he lost his grip on Seamus as well, and crashed back on the flagstones with an almighty "crack".
And didn't move.
"You've killed him!" stammered Seamus.
"Not quite". Ginny felt for a pulse, and found a light one. "Seamus, run for Madam Pompfrey."
Neville rose to his feet, looking down at the caretaker with a mixture of concern and guilt. "I didn't mean to. But he surprised me so."
He took off his shirt and wadded it under the caretaker's head. Ginny felt for the pulse again, and smiled.
"It's steady. I think he's just been knocked unconscious. But I'm surprised he went down so fast - Filch has always been the strong one..."
Her voice trailed off as she looked over her classmate beside her. Shirtless, the candlelight gleamed off Neville's new physique, giving a very clear view of the muscles he was now sporting. Broad shoulders topped the toned and sculpted torso, and Neville's slightly longer hair only accentuated the change in the previously-wimpy Gryffindor. His skin glowed with health, and his whole posture had changed – more upright, shoulders back, more confident.
"Oh. My. Neville."
She took a step closer, and gently ran her fingers over his chest.
"So that's what you've been doing by yourself all this time. No wonder he went down so fast. You're so ... buff..."
Neville smiled to himself. At last, all that positive thought had worked! He put his arms around Ginny, and started to pull her closer, her face looking up at his, her lips so close...
And then footsteps outside heralded the arrival of Seamus and Madam Pomfrey. Neville and Ginny jumped apart as if electrocuted, as the matron bustled in and took in the sight of Filch on the floor.
Madam Pomfrey moved her wand over the supine figure, shutting her eyes and chanting softly. A moment later, she looked up at the three and smiled.
"He'll be fine. A nasty headache, and a bit of a bump. But what...?"
She looked over at the writing on the wall behind the students, then back at their guilty faces.
"Oh."
Looking back at the caretaker, she shook her head, smiling even more broadly.
"Honestly, you three, shouldn't you be clearing up those paint buckets and brushes? And I think you should know that nasty bumps on the head can be the cause of minor amnesia. And I'll deal with that damned cat as well. But if you're not back in your beds in five minutes, it'll be points from Gryffindor - if indeed there are any left to be lost. Now go!"
With that, the matron placed her wand on Filch's forehead and muttered "Obliviate". Seamus grabbed the bucket, Ginny the brushes, and Neville gently removed his shirt from under Filch's head. Then they all ran back to the Gryffindor common room.
Seamus took the brushes and bucket to clean, and Ginny went to head up to her dorm. At the last moment, though, she turned back to Neville and kissed him hard on the lips in the way only his dreams had shown him up to now.
"I'm not coming back after the holidays", she said. "Mum says it's too dangerous, and is only using the hols as an excuse to get me home. But I'll miss you."
And she ran up the stairs to the girls' dorm.
And Neville headed up to bed with a smile on his face, and silently thanked The Secret for making his dream come true.