Originally written in December 2009 for the fandomcommerce Livejournal fic exchange.

Disclaimer: Everything you recognize belongs to JK Rowling; the rest is mine.

I had completely forgotten about this fic and it was a very pleasant surprise to find it in my hard drive yesterday. So I gave it a once-over and here you go.

I hope you enjoy. All comments are welcome and encouraged. I accept both signed and anonymous reviews.

James Potter had a mystery to solve.

It had recently come to his attention that Lily Evans walked funny when she was in the library. She took these big steps, occasionally – when carrying a heavy load – risking her balance.

First time he saw her walk this way, he became a bit puzzled. Second time around, he started to wonder and came up with a few – ridiculous, if he were honest with himself – ideas as to why she did it. Third time around, he had to ask.

"Is your arse chafed?"

"WHAT?"

"You're walking funny."

Lily threw him a nasty glare, then she turned around, her long, red hair flowing at the movement. "I'm fine," she said coolly and headed out of the library.

James stayed back, sitting at his desk and staring at her in bewilderment, as she now walked in an even weirder fashion – two really small steps, then one of those big ones, then two small steps again and so on.

"Maybe that's her silent walking," Sirius suggested, when James reassured him that he had made a point of following her around and she had only done that in the library.

"I don't know. It's not any more silent than regular walking."

"Maybe her arse really is chafed and she's embarrassed to tell you."

"But just in the library?"

Remus shook his head in dismay. "James, what do you care how she walks?"

"It's weird! It's making me curious!"

The boy didn't insist. He knew that, if James Potter had something in his head, it was impossible to get it out. He would not rest until his curiosity was satisfied.

"Do you need help stalking her?" Peter suggested.

James took a moment to consider it. "No," he said eventually. "I think I should do it myself, it would be more discreet. I'll let you know what I discover."

Sirius and Peter nodded their agreement. Remus just rolled his eyes.

And thus, for the past week or so, James Potter had been following Lily Evans around, paying specific attention to where she went and how she walked.

Ironically enough, since that library incident, Lily had been taking care to make sure she was going nowhere near James. But she would look around, see no one, and continue her way. How was she supposed to know James Potter was hiding around the corner, or behind that door left ajar, or up the next staircase, just outside her view?

During the time that he had been following Lily Evans, James Potter had made a few significant observations.

Number one: The library floor was the only floor in the rooms they regularly visited that wasn't carpeted. Instead, it was parqueted.

Number two: The library was the only room where Lily made a point of looking down while she was walking.

He would have believed that she was afraid of slipping on the parquet, except that her big steps seemed to do everything but that. In fact, they made her more prone to slipping.

Today, James made what, he was sure, constituted a key discovery.

The library floor was the only floor in the rooms they regularly visited that had a pattern on it. The floorboards were square shaped, in squares that were sized barely more than a Lily Evans foot.

James had camped behind a bookcase, waiting for Lily to pass in front of it as she would leave the library.

Indeed she did, and this time he was close enough to notice just how big her steps were.

Big enough to skip every other square.

Once she was walking with her back definitely on him, he crawled out of his hiding place and pressed his glasses firmly back on his nose.

He was certain that she had skipped every other square all the way out.

"What do you think you're doing, young man?"

Madame Pince had sneaked up to him, and was now standing over him, like a hawk ready to pry his eyes out.

"Uh, I... I was just going out," he said and before she could say another word, he scrambled up and left the library. After all, he was now on a mission.

He ran past Lily without acknowledging her; he was in a rush to get ahead of her, and she wouldn't pay much attention to him anyway. He knew she was going to the Gryffindor tower, and he knew her usual route, so he had a good opportunity to set up a test for her.

Once he was two corridors ahead of her, he stopped and looked around. Nobody was in sight.

He pulled out his wand and started to draw big squares on the carpet, roughly the size of a Lily Evans library step. He wasn't sure they would fool her; although he had a good hand for both magic and drawing, these yellow, ever-so-slightly lopsided squares on the periwinkle carpet couldn't possibly pass for ready-made.

Once done, he ran ahead and hid behind the half-open door leading to the next corridor.

A minute later, she was at the corridor with the painted carpet. He saw her notice the squares on the carpet and eye them strangely. Then, she started to walk in an irregular fashion; two regular steps, then one that would be either smaller or larger, depending on how close to a line she had come. She was still skipping all the lines.

James grinned to himself. Time for round two.

There were several people in the next three corridors that Lily would pass through, so James couldn't paint there. He got his chance at the fourth one, though.

He started to draw small squares on the carpet, just big enough for Lily's foot. Gradually, he made them smaller, and by the time he reached the middle of the corridor, he was bored enough that he settled for scribbling about, still making sure that there were no gaps big enough for Lily's feet.

When he was happy with his handiwork, he found an unlocked, empty room in the corridor and hid behind its door. He left it just barely open, but that gave him ample view to the corridor.

Lily came in less than a minute later. She frowned massively at the sight of the painted carpet, then began to make her way to the other side of the corridor, very carefully placing her feet in the squares James had allowed.

With every step, her job was getting more difficult, until she reached a square that was decidedly too small for her foot. First she tried to fit it in, without stepping on the line, then she resorted to tiptoeing. One, two, three steps...

Her schoolbag fell from her shoulder, landing right next to her. Lily tried to reach for it, but it was too difficult to kneel while standing on tiptoes only. She carefully tiptoed back to where the squares were big enough for her to step down, picked it up and continued as previously. All the while, James watched her in amazement, wondering how long she'd last.

Eventually, she reached the scribbled part. She made an attempt to continue tiptoeing ahead, but soon she realised she wouldn't find a path among those thickly drawn lines. Sighing in defeat, she dropped her schoolbag on the floor, right behind her, and sat on it to rest.

James thought it was time to make an appearance.

"Oi, Evans! Got a date?"

She turned at him, her eyes narrowing. "Don't be ridiculous."

"Just kidding." James smiled pleasantly as he made his way close and then sat on the floor, right opposite to her. "So what are we waiting for?"

"Nothing," she said grimly.

"What are we doing?" he tried.

Lily shook her head.

"Well, I'm leaving, then." He rose and turned around to leave, but when he realised she wasn't even bothering to move, he turned back to her. "Oh, come on, Evans, just tell me what you're doing there!"

"You're very curious, d'you know that?"

"What would you do, if you saw me sitting down in the middle of a corridor?"

"I'd assume you're being your usual silly self."

James did not talk back, instead took the time to study her face. "You don't look all right." His tone was serious now. "Are you sure you don't need any help? Merlin knows it would be the easiest thing in the world to leave you here and go find my friends."

She avoided his gaze. "Then do that."

He sighed. "Lily?"

She ignored him.

"OK, get up."

"No!"

He tried to grab her hands, but she was wrestling them away.

"Come on -"

"Let go of me!"

"But Lily, for Merlin's sake -"

"What's wrong with you, just leave me alone!"

He gave her a stern look. "Lily."

She countered his look.

Quickly making up his mind, James ran behind her and, before she could stop him, grabbed her schoolbag forcefully.

She landed with her bottom on the floor and her feet stepping on lines. She looked at them, horrified, and any anger towards James – oh, there was sure to be plenty of it – was forgotten.

She burst into tears.

"Lily!" James dropped her schoolbag and knelt next to her. "What's wrong?"

"Go away!" she said, between sobs. "Look what you've done!"

"What did I do? Lily, come on... Whatever it is, it can't be so serious. Look!" He picked up her schoolbag. "Here's your bag, I swear I didn't break anything."

"Just go away!"

James didn't. He was determined to stay there until she'd be well enough to get up and go to the Common Room.

"Will you please get away? You're unnerving me."

James scooted a bit farther. "How's that?"

"Better..."

She was done crying now, but her face was still red as she blankly stared at her shoes.

"OK, so what was that?" James asked, after a couple of minutes had passed in silence.

Lily did not meet his eyes as she answered in a small voice, "Lines unnerve me."

"What lines?"

"Lines on floors. I can't step on them."

"Why not?"

"I don't know."

"What happens if you step on one?"

"...I don't know."

"You mean you're fourteen years old and you've never stepped on a floor line?"

She nodded.

"What do you do about those floors with the tiny tiles?"

She sighed. "When I was eight years old, my parents took me and my sister to a swimming pool, to learn swimming. The floor around the pool had these tiny tiles all around."

"And what did you do?"

"I refused to go anywhere near it. My parents thought I just had a big fear of water and didn't insist."

James couldn't suppress a smile. Lily missed it, though; she was still staring at her shoes.

"You're stepping on lines right now," he pointed out.

"I know."

"What are you going to do about it?"

"I don't know."

"What about realising there's nothing to be afraid of?"

She shuddered. "I'm not afraid. It just... feels wrong."

"It's just a pattern. Look." He rose and walked to stand opposite to where she was sitting. "Look at me."

She looked up to him.

He offered her his hands. "Get up. Don't look down, just look at me and get up."

She took his hands and did not miss his eyes as he helped her up.

"Nice," he said. "Now we're going. Don't miss my eyes, I'm watching you."

He walked backwards and she walked forward, her green eyes fixed on him. James found himself enjoying it.

Once they were underneath the archway leading to the next corridor, he let go of her hands and smiled widely. "See? Piece of cake."

She blinked. "My bag," she remembered.

"It's right there, go take it."

She turned and looked at the bag, sitting in the middle of the corridor, surrounded by yellow lines.

"Come on," James poked her. "It's all in your head."

Lily took a deep breath and sprinted back, picked her bag up and returned to James.

"How did that feel?"

She shuddered. "Weird."

"You'll get used to it. There are weirder things in the world."

She looked at him closely. "You bet."