Marty remembered the terrifying time he'd changed the world. He tried not to dwell on that reality now that it was over - his dad dead, his mom trapped with Biff, Hill Valley a post-apocalyptic shithole - and there hadn't been much time in the moment to dwell, either. He and Doc had just enough time to think up a plan and set it in motion, and that's when Doc dropped another bomb on him.

"We'll have to move quickly," he said, opening the door into the night air; the last of the rain was falling, and Hill Valley smelled musty. "I'm not sure how much time we have."

"Time? What are you talkin' about, we've got a time machine!" he pointed out.

"No, no, not that kind of time," Doc said, wrenching open the gull-wing door and barreling inside. Marty followed. "A reality like this can only be stable for so long - in this reality, there is no time machine. I never got a chance to invent it! That means there's no way for Old Biff to travel back in time and give himself the Almanac in the first place, meaning this reality cannot exist!"

"Jeez," he said. It hadn't sunk in then. "Heavy."

"I'd say we're protected for the time being by virtue of having been displaced from our own time when the change occurred," Doc went on, shaking his head. "But it's only a matter of time before the bubble bursts."

Marty hadn't thought about that bubble in a long time, but he felt it get smaller during his first year of college. His parents wanted him to stay in state, but in a huge state like California it was easy to get far away. He'd felt a pull to leave Hill Valley, to get out there and see what he could do. And so far, he was really thriving at UC Santa Cruz; part of him wondered if he would have always done well in a new place if it hadn't been for the multitude of new places he'd been forced into a year before.

A year, he thought as he neared his first long weekend. It had been an entire year since he'd gotten back to 1985 permanently. Well, until he got to 1986.

His mother called him often, and he knew he wouldn't be able to get out of coming back down for a visit. Everyone was eager to see how he was doing, and he really missed them. He missed them a lot.

So why was he parked at a 7/11 three blocks from Lyon Estates instead of on his way home?

He slumped against the steering wheel, watching people come and go. He recognized some of them, he realized, but they were thirty years older than he remembered them. He never got that feeling in Santa Cruz.

He made a decision. Giving himself a countdown from three, he got out of the car and walked towards the payphone. The cold October air bit at him, and the bright green light of the store made the night around him seem even darker. He slipped a couple quarters into the payphone, dialed the number, and waited.

"Hello?"

"Mom, hey, it's Marty," he said, and cleared his throat. "Uh, so I'm gonna get into town later than I thought I would."

"Marty, it's almost midnight!" Lorraine almost scolded. "Where are you?"

"I'm still at least two hours out." He huffed out a laugh. "I just… lost track of time, I guess."

She hummed disapprovingly. "I don't like you driving this late."

"Mom, c'mon, I'm fine. I'm already on my way. I got coffee," he lied easily. "Don't wait up for me, okay? It'll be late."

"Okay," she answered, in a tone that made him think she might be considering waiting up anyway.

"Seriously, you don't have to," he implored. "I'll be back when you wake up!"

"Okay, big college kid," she said, laughing. "I hope I recognize you!"

Marty's breath hitched. "Yeah, you too."

—

It was easy to think of the last few months as a hiccup, a fluke. He had started to gain memories of the new timeline, but they blended and muddied his old ones, to the point where he got afraid to think of the past at all. Once he was gone from Hill Valley, he started to think of his past in broader terms. When he thought of home, he thought of the reality where he had spent most of his life.

And he couldn't go back. So he kept driving, towards the only place he could ever find shelter in the middle of the night.

Well, the second best place. Doc's garage was a glorified - actually, it was an actual storage closet these days. When he came back, to the spring of 1986, he had fixed up a dilapidated farm house on the outskirts of town. Not only did it have enough space for him, Clara, and the boys, but he had converted the barn into a spacious workshop. Marty wasn't one for rural living, especially after getting up close and personal with late 1800s latrines, but he had to admit it was pretty swanky. He checked the clock. 12:08. Maybe he'd be awake. If he wasn't, he'd just crash on the couch.

He couldn't stop yawning as he drove, but eventually he saw the beacon of Doc's workshop light at the end of the aggressively dark road. He didn't know why he was worried; even with all the possibilities of the multiverse taken into account, none of them had Doc asleep at a reasonable hour.

He pulled into the driveway as quietly as he could, knowing that Clara, Jules, and Verne were closer to regular human beings that would be asleep by now. When he entered the lab, he smiled at all the familiar junk in a new location. The barn was bigger than the garage, but Doc's clutter was like a gas that fit to the shape of its container.

Doc himself was hunched over a work table, goggles on, tinkering with something Marty probably couldn't begin to understand. He approached gingerly, not wanting to startle him. "Hey, Doc?"

He barely looked up. "Marty, welcome," he said, then gestured to the end of the table. "Hand me that sauntering iron, would you?"

He did. "What's that you're working on?"

"Oh, it's a continuation of sorts," he said. "You remember my electric tire iron, yes?"

"Jeez, how could I forget?" He sat down across from him and rested his chin on his arms. "That thing got me good."

"It had quite a few safety issues." He fiddled with his goggles, and Marty realized they were magnifying lenses. "I'd gotten to a bit of a standstill on it, but I happened upon a flexible type of ventilation system developed in the early 2040's that should take care of the overheating issue, and that might-" Doc stopped short. He wrenched his goggles up, stunned, and would have thought he got electrocuted if he wasn't smiling. "Marty! What are you doing here?"

Marty laughed, an unexpected wave of relief washing over him. "Long weekend," he said. "Mom and Dad wanted to see me and find out how college was going and all that stuff."

"How is it going?" He smiled wryly. "How are you liking Calculus?"

He sighed heavily, laughed again. The Applied Physics minor had been his own idea, surprisingly enough. Less surprising was Doc's encouragement. "It's hard."

Doc sighed almost dreamily. "I remember undergrad." His gaze drifted toward the window, and he stood with such urgency that Marty couldn't help but follow suit. "Great Scott!" He checked one of his watches. "It's one in the morning!"

He looked around, stuck his hands in his pockets, and shrugged. "Yeah?"

"Well, what are you doing here at this hour? You should be at home, in bed!"

"You're one to talk, Doc," he said, sitting back down.

Doc waved his criticism away and started rummaging through his toolbox. "My time management skills aside, you could've easily come to visit me during the day tomorrow. Clara would love to see you, and the boys never stop talking about you now that I've let them start skateboarding." He found whatever he was looking for, evidently, and started fiddling with the tire iron again. "How's your pop, by the way? He called me to fact check something for a new manuscript, and I wanted to get back to him. Did he mention anything about that?"

"Uh, I dunno," Marty said through a yawn. "I mean, I'll ask him when I see him."

"You haven't seen him?"

Marty woke up a bit more. "I… I hadn't gotten to-"

"Marty, you have been back to see your family, haven't you?" He set down the tire iron.

It was one of the few times Marty didn't feel capable of handling Doc's full attention, so he got up again. "I mean, not yet, but they're all there. I can go whenever, right?" The tiredness was disarming him and he knew he wasn't making any sense; he paced back and forth to try and keep his brain moving. "Just 'cause I don't wanna go home now doesn't mean I… don't wanna go home eventually."

Doc nodded, but looked as if he wanted to shake his head. "If something's bothering you, you can-"

"Everything's fine," he said quickly, but he knew he was being ridiculous. Ridiculous, and ungrateful. His perfect family was at home, and he'd forsaken precious time with them for no reason.

"Marty," Doc said quietly, and he knew it wasn't because of the late hour, "having trouble adjusting after what you went through is normal."

"I'm not having any trouble," he said, then sat down again, exhausted. "Everything's amazing. It's like… like I'm living in a dream." He rubbed at the sleep in his eyes. "A really good dream. But…" He flailed his hands, unable to find words but just as incapable of stopping himself from talking. "I dunno, Doc, no matter how good a dream is, you eventually wanna wake up, right?" He wished the restless energy would go into his brain instead of his body. "But that sounds awful, y'know? Like everything we did was all for nothing. But I just-" He shrugged. "I just feel guilty, okay?"

"Marty," Doc said; he had gotten up and crossed to the other side of the table at some point. He put a reassuring hand on his shoulder. "Out changes to the timeline-"

Marty swatted his hand away. "Stop!" He got up and took a few steps toward the window, trying to ease his claustrophobia. He saw the Time Train sitting in the field, an imposing and improbable shape in the dark. "I don't want you to- to think I don't-"

All sound died in his throat. The silence hung thick and heavy. Marty could hear the whine of the too-bright lights and the humming of a million machines. He crossed his arms around himself, attempting to get his thoughts collected and figure out what he was trying to accomplish. He wished Doc would go back into the house to be with his family, go to bed, and let Marty mope in the workshop all night by himself.

He didn't realize Doc was next to him until he spoke. "I'm not sure exactly what it is you're feeling," he said gently, "but I do know there's no one else who could understand you situation more than I could."

Marty's shoulders slumped. He nodded stiffly, then chanced a look over at Doc, who looked back at him encouragingly. "Doc… do I seem like a different person to you? Like, since I came back to 1985 the first time?"

He furrowed his brow. "What makes you think that?"

He pushed through the tightness in his chest. "When I came back, when I went to the mall parking lot-" He faltered. "I, uh, got there earlier than you set the time circuits for. I saw myself go back to 1955. But… that wasn't me, right? That guy always lived in this timeline, with all the changes I made. So…" He gulped. "Where did he go?"

"Amazing," Doc muttered. His eyes bugged out like they did when he was thinking. "Perhaps returning to the present before your past self has left it could cause a closed loop of sorts, or maybe some sort of alternate tangent-"

"I stole his life," Marty realized with dull horror. "I don't belong here, do I? I knew it!"

"No, no, that's not what I- I was simply working through a problem-"

But Marty couldn't stop now that he had finally grasped it. He sprinted to the other side of the workshop and started rummaging through a drawer. "There's gotta be something we can do, Doc! We could- we could get in the train and go back to 1955 and- and-" His hands closed on the keys, and he held them up.

"What? Marty, you're not thinking clearly!" Doc raced to meet him, grabbed his arm, and tried to wrestle the keys from him. "Besides everything else wrong with your reasoning, the only thing you'll find on this spot in 1955 is a bunch of farm animals and a family that's not expecting to be woken up by a flying train!"

Marty grabbed for them. "You said it yourself, Doc!" Neither of them could get a tight enough grip. "It's only a matter of time before-" The keys clattered to the ground, and Doc got to them first. He clenched them in his fist and held them away from Marty, his expression hard. "… Before the bubble bursts," he finished lamely.

Doc's expression softened a fraction. He brought a hand to his forehead and looked up at the ceiling, then took a long breath in and out. This was just enough time for Marty to feel embarrassed. He slowly reached out and pushed the drawer shut, feeling a need to somehow repair the damage he had caused.

"Come, sit down," Doc finally said, guiding him to the couch. "Let me get you a glass of water." Marty leaned back on the couch, eyes burning with sleep. He wondered if he could make himself fall asleep before Doc got back, but it was no use.

Doc sat down and handed him the water. He took a polite sip and placed it on the side table. Doc asked, "You haven't spoken to anyone about this, have you?"

"Jeez, Doc, of course not," he said. "You think I'm stupid enough to tell anyone about-"

"No, no, that's not what I meant," he said, but there was no impatience in his voice. "I mean, you've been sitting with these feelings for a while now? You haven't worked through this with anyone?"

"What, and let 'em cart me off to some loony bin?" He paused, then shook his head. "I just can't make myself okay with it, Doc," he said quietly; he didn't want to admit it, but he felt like he was never going to get another chance to say this out loud. "My family - it's like they're totally different people. And- and I know they can tell I'm not the right Marty. How am I supposed to- to go home and pretend it's all fine?"

Doc seemed to consider his question like it was a math problem. He reached toward a shelf and grabbed a notebook and pen. "Imagine that this circle…" He drew a circle. "… Represents your father." He scribbled the letter G inside of it. "And this line represents the events from 1955 to 1985 as they originally occurred." He drew a line. "And this line…" He drew another, parallel to the first. "… Represents the events after our interference. Are you with me so far?"

"Yeah, yeah, I get it," he said, eyeing the lines with growing dread. He braced himself for the bad news, that he'd hopped lines with no hope of ever going back.

Doc looked at him purposefully, then drew another line. And another. And another. He covered the page in scribbly lines branching off from the original circle - intersecting, uncontrolled, and careless. "These lines represent everything that could have possibly occurred from 1955 to 1985. Paraphrased, of course, as I doubt there will ever be enough paper in the known universe to accurately portray every tangent. But you understand what I mean," he said, looking Marty in the eye. "There are infinite potentials, consequences, reactions - but the subject…" He pointed at the circle with the G in it. "… Is still the same at its core. Replace that with your mother, your brother, your sister, you - you're the same person in the midst of all the possibilities."

Things in his head were starting to feel considerably less jumbled. But still - "What about the other Marty?"

Doc shrugged, something Marty was not used to seeing. "Perhaps the Ripple Effect hadn't caught up with that particular outcome yet, or maybe every potential exists at the same time in the same space, and you accidentally saw one of them. Either way, you'll drive yourself crazy trying to understand all the intricacies of time travel." He glanced in the direction of the house, and when he spoke, his voice was soft. "If there's one thing Clara, Jules, and Verne have taught me, it's that things rarely happen the right way. Clara's continued existence went against every preconceived notion I had of time travel - and that's before considering Jules and Verne, children of parents who, in the 'right' timeline, are deceased and separated by nearly 100 years. You'd think our bubble would have burst by now. But here we all are, for better or worse."

The idea that the universe was more resilient that he thought - that he could just let things go - hadn't occurred to him. Maybe he belonged more than he thought he did. Relief flooded his body, or his tiredness was finally catching up with him. Maybe he was just sick of thinking about it. Either way, he was more relaxed than he'd been in months. He rubbed at his eyes. "Mostly better."

"I'm glad you think so," Doc said, and put a comforting hand on his shoulder again. This time, Marty didn't shove him off. "I'm sorry for not thinking of this sooner. It was careless of me not to think-"

"No, Doc, don't worry about it," he said, hopefully firmly. He was starting to become one with the couch. "It's not your fault I can't think fourth-dimensionally."

Doc chuckled. "You've been making great strides as of late." He seemed to pause, then added, "I'm very proud of you, Marty."

That woke him up a little. "You are?"

Instead of answering, Doc hugged him. It occurred to Marty that, even if he wasn't totally okay right then, it didn't mean he wouldn't be okay eventually. The universe was always changing, after all.

He must've fallen asleep, because next thing he knew he was horizontal on the couch, a blanket draped over him, and a blonde kid was screaming in his face. "Marty! Jules, Marty's here!"

Marty propped himself up on an elbow, blearily looking around. "Verne! Mornin', buddy."

"Marty, after you wake up can you teach me how to skateboard? Dad said I could!"

He got his bearings, a burst of momentum getting him to his feet. "I'll be back later, alright?" He stepped into his shoes, shrugged on his jacket, and started towards the door. "I've gotta get home."