For my most beautiful better half, my dearest Sam. I had to post this today, because it's today so how could I not, so because of that, this is a little different than I originally planned. This is the main chapter, the next chapter will be a follow up (so also pre-season 1), and the rest will be a series of post-eps and episode AUs in this universe. I don't know how many chapters there will be.

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Spencer was fascinated by his thread from the first moment he noticed it. It strung out from his right pinky finger, out into the distance, stretching way, way North and East, too far for him to see where it ended. It stayed right there, right in that direction, always.

Spencer, being the child that he was, charted out the azimuth of the line, marked an arc for a margin of error, and examined the map carefully.

He could rule out close proximity by sheer fact of it not changing angle. Beyond that, though, he had no way of definitively narrowing it down. It could be any one of a thousand small towns or big cities in that arc. It could be any one of the millions of people who live within them.

For the moment, it became enough that the thread is a happy red.

When Spencer turned 5, things changed. The thread, which had wandered between a happy lava and a concerned scarlet, started darkening rapidly, landing on a color Spencer couldn't and didn't want to name. It resonated scaredangrysorrypleading and it hurt.

But when Spencer tried to convince someone that they needed to help, that they needed to do something, his father wouldn't listen and his mother was having a bad day and Spencer didn't know what to do. His threaded was hurting and he didn't know how to fix it.

Spencer Reid, at five years old, stole his father's debit card, took it to an ATM, withdrew five hundred dollars and then used the card and a pay-phone to book the soonest flight in the right direction — Detroit, Michigan.

He told the lady at the desk that his grandparents were in Detroit and that he was going to visit them. She told him it was policy that she needed parental permission.

Much as he hated doing so, he screwed up his face and pretended to cry, sobbing about missing his flight and never getting to see his grandparents. It was exactly as effective as he thought it would be. The woman let him right through. Through security he stuck purposely close to the family in front of him, making sure his gaze flickered to them often, as though making sure they were still there. He wasn't stopped.

He sat beside a family in the boarding area, slipped right behind them in the boarding line, and made his way onto the plane without further difficulty. His leg, though, didn't stop twitching until the plane was in the air.

Once it was, he settled back against the seat and resigned himself to a four hour flight of boredom.

Spencer had the sort of mind that, faced with a complete lack of stimulation, would drive him mad. Faced with such a cheerful option, he asked a flight attendant for a map and a pen.

Carefully, he charted the arc of their flight. He asked the flight attendant about wind speeds and pressure variations along their path. Bemused, she answered vaguely until Spencer interrogated her for specifics. He used this information to mark the times that they would be at each interval of the arc. He shaded in his originally calculated area. Then, at each fifteen minute interval, he charted the angle of his thread using his compass (the one he'd started carrying in case his thread ever moved — it never had, but now he was moving in relation to it). Charting the changes in angle as he moved along the arc made things simple.

By the time he landed in Detroit, Spencer knew where his threaded lived, because all the lines converged in one place — Chicago. The only problem with that, was that nearly 10 million people lived in the greater Chicago area, and Spencer had to locate one.

First, of course, he had to get there.

Figuring there was no use in changing what had worked once, he booked the flight over the phone again.

This time, though, he took one look at the man behind the desk and he knew that crocodile tears weren't going to work twice.

He found the computer area for traveling businessmen and painstakingly typed a letter in his father's voice, granting him permission to fly to see his grandparents in Chicago. When it came out of the printer, he signed it, mimicking his father's signature exactly from memory.

The man at the desk took the letter without issue, filed it, and gave Spencer his ticket.

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Spencer used the plane's trajectory over Chicago proper to narrow down his search area to the South Side.

He took the blue line L train into downtown Chicago and then transferred to a southbound red line subway, paying for the tickets easily with the cash he had on hand.

He took the train until his thread was pointing straight east and got off at the next stop.

It was almost three days after his thread had gone dark. Spencer was exhausted — having slept only in fits on planes and hard airport seats — which he knew wasn't the safest state of mind when wandering straight through gang territory that he was completely unfamiliar with, but at this point, nothing was going to stop Spencer from finding his threaded. He wasn't sure how he was going to help, but he intended to try.

Five blocks from the L, he was stopped by a kid at least twice his size. "What're you doing here, squirt? You don't belong."

Spencer looked him in the eye. "I'm finding my threaded. Trouble is brewing."

The kid looked at Spencer's right hand reflexively. "How can you know that sort of thing?"

"I'm thread sensitive. For example, you haven't met yours yet. But don't worry — she's quite content, for now."

The kid gave Spencer a skeptical look. "First part was a lucky guess. Second could be a lie, all I know."

"Please." Spencer was not afraid to swallow his pride for this. "Please. I only want to find my threaded, to help. Besides, what damage could I possibly do?"

The last line seemed to get through, because the kid shrugged and let Spencer pass.

The sky grew darker and darker. Spencer had begun his trek in fading light, but it was rapidly darkening. Raised in Las Vegas, Spencer knew the streets weren't the best place to be in the dark, but he didn't know where to stop, so he kept walking, kept following his thread, and kept to the shadows.

Almost two hours and about fifty strange looks later, the sun was gone but his string had finally stopped. He walked all the way around the house to confirm it. His threaded was inside this house.

Spencer didn't know how to act. Didn't know what the right thing to do in this situation. Didn't know exactly what time it was, even — only that it was late.

So, naturally, he knocked.

After a long pause, a woman with chaotic brown hair opened the door. She blinked at him.

"Hello?"

"Hello," Spencer said. "I'm following my thread, because it looks unhappy. It led me here."

She blinked again. "Oh." She looked down at his thread, which did indeed stretch into her house. "Well, you'd best come in then."

The woman introduced herself as Fran Morgan and immediately set the coffee machine. She seemed rather astounded when Spencer told her he'd come from Vegas.

"Alone?"

"No one would take me. But it wasn't right; I could feel it. It wasn't right, and I had to fix it."

"What do you mean, it wasn't right?"

So Spencer had to explain his thread sensitivity again, and how the color had gone wrong, because he didn't know how else to describe it.

"Please, can I just... Please."

"It's the middle of the night!"

"But it still isn't right. I want to help."

But Fran Morgan shook her head. "Tomorrow. For now, we're all going to get some sleep."

She laid out blankets on the couch for Spencer and kissed his forehead, seemingly out of habit. "Sleep, child. You're safe here."

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Spencer awoke to the sweet smell of syrup and the sound of Fran humming in the kitchen.

She smiled at him, asked if he wanted any pancakes, and then said, "If it's Derek, you'd best not tell him. Sarah and Desi are total romantics about the threads, but Derek hates them."

Spencer was the one left blinking this time, but he nodded and asked how he could help with breakfast. He was setting the table when other children started filing in.

The first was, apparently, "Desi."

"Mama, why is there a scrawny boy at our table?"

"Be nice, Desiree!"

"Yes, Mama. Mama, why is there a strange boy at our table?"

Fran rolled her eyes, but she was laughing as she did so.

"He's following his thread, Desi."

Desi turned to Spencer. "Why're you following it so early?"

Spencer shrugged. "It's a long story."

Desiree looked like she wanted to asked, but instead she just started helping him set out glasses. Spencer looked at his thread. It still stretched into the house.

The next one to walk into the kitchen was Sarah. "Oh, Lord," she said. "Better not tell Derek." She was staring at his thread.

"Better not tell me what?"

And there he was.

Derek Morgan was about twice as tall as Spencer, and probably over twice his age. And he was looking right at him. "Who's this?" he asked, as he immediately took half the plates from Desi and finished placing them around the table.

"This is Spencer. He's going to be here until his parents can pick him up."

"And how long is that going to be?"

"I don't know yet, Derek. They're a long way away right now."

Derek looked up from the water he was pouring into glasses. "Then how did he get here?"

In reply, Fran put a plate of pancakes in the center of the table. "Breakfast now. Questions later."

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Fran, Spencer soon found, was a force of nature. In a shorter span of time than Spencer would've thought possible, she had three children ready for school and herself ready for work.

Then she stopped. "Spencer, do your parents know where you are?"

"Not exactly," Spencer said honestly. By this time, his father probably knew that his credit card was missing and had been used to purchase flights to Chicago.

"You have to call them."

Spencer shook his head. "They won't care, ma'am."

Fran looked at him sternly. Spencer shrugged. "They won't. Mom's in the middle of an episode; they can last for weeks. Dad probably figured out his credit card was gone before he noticed that I was."

But Fran insisted and Spencer knew better than to think he could stay in this place forever, so he called. His father answered. That meant his mother likely wasn't lucid.

"Spencer? Spencer, where the hell are you?"

"Chicago."

"I know that much! Why the hell are you in Chicago? Why did you take my card?"

"I had to get here, didn't I?"

"Did you, now?"

"Yes!" Spencer said. "I told you! I told you, but you wouldn't listen to me!"

"Spencer, you'd better get your ass back here. As soon as possible."

"All right," Spencer said, and he hung up. "He says I can stay."

Fran gave him a skeptical look, but she didn't know what was going on, didn't know why Derek's thread should be hurting when he was just up at the cabin with Carl Buford, fishing. Derek admired Carl. It didn't make sense. If Spencer could help her son, well, then he could stay for a little while. Just a little.

When Derek came back down, Fran said to him offhandedly that Spencer was coming with him to school.

"What? Mama, why?"

"Well, he can't stay here alone all day, now can he?"

"What about Desiree or Sarah?"

"Derek." Her voice was stern, sharp as steel. "It was not a question."

Spencer, not wanting to be seen as an obligation, said quietly, "I can stay here."

Derek looked at him, really looked at him for the first time. He rolled his eyes. "No. I mean, whatever. It's fine."

Spencer smiled, easy and bright. Derek's gaze lingered for just a moment, seemingly puzzled, before he shook his head and grabbed a pencil case off the floor and stuffing it into his backpack. "Well, come on then. We need to leave now if we don't want to be late to algebra." Derek made a face, but Spencer smiled again.

"I like algebra," he said. Derek looked at him.

"What sort of five year old knows algebra?"

Spencer shrugged. He'd been making his way through the curricula of a typical junior high student this year. "It's better than geometry," he said. "Geometry is boring."

Derek scowled as he held the door open for Spencer, but it was teasing. "I happen to like geometry!" he said in mock offense.

Spencer grinned again. Today was going to be fun.

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In algebra, Spencer was patient. He watched from the desk beside Derek's, ignoring all of the odd looks he was getting. His feet swung back and forth. He couldn't stop grinning.

Finally, the teacher asked a question that seemed to have stumped a majority of the class. No one wanted to volunteer. Spencer raised his hand. The teacher raised an eyebrow.

"Yes?"

"May I solve it?" Spencer asked.

The teacher looked doubtful, but he looked around and seemed to give up on the rest of the class even attempting. "Go ahead."

Spencer turned and hopped out of his desk. He walked up to the board, took the chalk, and then pulled an extra chair from near the wall. He climbed on top of it, ignoring the titters from the class.

In less than a minute, he had the problem on the board with complete work and the answer circled. He hopped off the chair and pulled it back, and returned silently to his seat. Derek was gaping at him. The whole class was gaping at him.

The teacher seemed to recover himself first. "That is… correct, Mr… um."

"Reid," Spencer offered.

"Mr. Reid," the teacher repeated. He blinked a few times before shaking himself and launching himself into and explanation of exactly what Spencer had just done.

Derek was still staring at him. Spencer shrugged. "I told you I like algebra," he said.

Shaking his head, Derek muttered, "You are one weird kid."

.

When they returned from school, Spencer was no closer to finding what had made Derek's string go dark, but he was watching it lighten. Not by much, not enough, but just a little.

Spencer understood people. He knew how they worked. He very much wanted to give Derek a hug, but he knew no thirteen year old boy would accept a hug for his own sake. He might, however, give one for the sake of a five year old.

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When Fran came home, she was very surprised to see her Derek on the couch with a sleeping five-year-old in his arms, a Bond move on the television. At her look, Derek gave a sort of half shrug and murmured, "He got lonely."

Fran hid her smile behind her hand as she moved into the kitchen to start dinner.

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After dinner, Derek found out that Spencer had never played basketball before and he took the five year old outside to shoot at the hoop in their driveway.

Fran wondered about it — Derek hadn't played in their driveway for years, preferring the court at the center — but she marked it down to Spencer's presence and Derek's pride. Spencer, as Derek soon found out, was a genius when it came to strategy but terrible at implementation. He could reel off the exactly angle that the ball needed to be released and with what degree of force, but he struggled to get the ball to do that.

When they came back inside, Spencer was flushed, both of the boys were coated in a layer of sweat, and both of them were grinning.

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Derek woke up in the middle of the night and almost panicked at the sensation of weight on his chest. It was only the rapid processing of the lightness of the weight that stopped him from throwing Spencer onto the floor. The kid was curled up into him, head pillowed on Derek's chest, on hand fisted in Derek's shirt.

Derek measured his breaths, feeling them slow gradually, staring at the kid on his chest. Spencer was strange. And Derek was pretty sure he'd started out sleeping on the couch. But somehow, Derek didn't much mind. Spencer was light and warm and his breaths were soft and… And he was nothing at all like Carl. Derek didn't feel pinned, he felt… protective, not that he was going to admit that to anyone.

Derek put a hand lightly on Spencer's back and fell back asleep.

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Three days later, Spencer went home. He didn't want to, wasn't satisfied with the new red (almost the color of fully oxygenated blood after it clotted), despite the improvement. Derek hadn't told him what had changed to make it that sickening shade, but Spencer strongly suspected he wouldn't, even if Spencer told him about the threads, told him that he knew something had happened.

But Spencer's father had redialed the number that Spencer had called from several times in the last hour, clearly fed up with his son's continued absence — or, perhaps, his credit card's continued absence.

Fran put him on the quickest plane home, after that. Spencer, though, could see in her eyes when she took him to the airport that she wasn't sure she wanted him to go — she could see that something was… off, in Derek, and Spencer's presence helped, somehow.

But Fran was still convinced that Spencer's parents were missing him, so she made sure he made it through security and stayed to make sure he didn't slip back through before his flight left.

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Spencer's thread began to make him sad. He could tell that Derek was hurting, and every once in a while he could slip away and make his way to Chicago, but his father started watching him closer, and it became, though not impossible, very difficult.

Then, when Spencer was seven, almost eight, the thread stopped turning sickly red. It wasn't a sudden thing. Over the course of several months, the thread graduated from the sickly color it had been for almost three years to a muted, subdued, but less unnerving shade. It was colored guiltreliefsorrysorrysorry. But that, too, faded as the months passed.

And life went on. Spencer graduated high school at age twelve, went on to college while staying with his mother. His father left. He baffled his classmates by knowing absolutely nothing about sports — with the sole exception of Northwestern University's football team.

He lost track of Derek after an injury takes him off the football field and out of the news. Spencer didn't allow himself to worry, though. He knew they would find each other again.

He earned his first BA — Psychology — and, without any idea what to do next, went on for a Ph.D — Chemistry, for variety's sake. After all, for complete brain usage, diverse stimulation was key.

Years later, Spencer found himself at the FBI Academy with only half a clue how he got there. He didn't know what to do with his life and Agent Gideon was rather persuasive. Beyond that, he wasn't even sure why he was there. The idea of him as an FBI agent was laughable, at best.

But Gideon wanted him, and Spencer got the feeling Gideon was not a man often denied the things he wanted and could achieve through sheer force of will. So he made his way — poorly — through the Academy and somehow wound up licensed and offered a job with the BAU. The Behavioral Analysis Unit. He couldn't turn it down, no matter how much he was still convinced he'd wash out in his first year.

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Walking into the BAU on his first day was… surprising, to say the least. He'd known Derek was nearby, because the string managed complete circles at times, but he wasn't expecting…

"Derek?"

Derek's head snapped up and toward him. Spencer watched surprise wash across his face. "Spencer?"