It wasn't easy for Dipper and Mabel, returning to California. So much had happened over the summer, and their entire perspective had changed.
At school, they had no one… not even each other. The twin's plan to stand by each other on the harrowing path to adulthood went out the window when they found out their school had a new principal. On the first day, just a week after their return from Gravity Falls, Dipper and Mabel were unpleasantly surprised when the received their class schedules- and found that they wouldn't be spending a single class together that year.
Turns out their new principal felt the twins were "overly-dependent" on one another; that each of them needed to learn to stand on their own two feet. The result was that they had to endure the horror of middle school alone. With no friends, and the bullies tormenting them worse than ever, school was becoming unbearable.
Their parents weren't much help. Mr. and Mrs. Pines had enjoyed their summer alone a little too much, it seemed… now they were almost never around, leaving their children in the care of their grandfather, Shermy Pines. He was like Grunkle Stan, only a lot more grouchy and a lot less fun. He spent most of the day sitting in front of the TV, occasionally barking out orders for the kids to get something for him, or otherwise complaining about his elder brother and how he "couldn't believe their parents let them spend the summer with that no-good swindler".
Mabel almost said something to him, but Dipper stopped her; it wasn't a good idea to get Shermy mad. They found that out the hard way when they were little.
Days passed. Days turned to weeks, weeks turned to months… and all the while, Dipper and Mabel reminisced about Gravity Falls. He thought about her all the time, longing to be reunited with his crush. Mabel spent all day in her room with Waddles, flipping through her scrapbook, reliving the best of her summer memories and thinking about her friends.
Finally, the Christmas holidays arrived. As always, it was to be just Dipper and Mabel, alone with Grandpa Shermy. Their parents were planning on going skiing. They wouldn't be getting any Christmas presents this year; Mr. and Mrs. Pines had been getting complaints of the twins "misbehaving" in school, and that their grades were slipping. Neither of them listened when Dipper and Mabel told them that they were feeling depressed, that they missed all their friends in Gravity Falls- the parents were starting to agree with Shermy, that Grunkle Stan had been a bad influence on them.
No Christmas decorations, no presents, and their parents had abandoned them yet again. The twins agreed; enough was enough.
Piedmont, California was not their home anymore. "Home is where the heart is", that's how the saying goes… and Dipper and Mabel had left their heart behind in Gravity Falls. With Stan, and Ford, Wendy, and Soos, and all their friends. Their real family.
Unbeknownst to Mabel, Dipper had saved one of McGucket's memory guns, and smuggled it home. He unveiled it to her one night, just a few days before Christmas Eve. Mabel immediately understood what he wanted to do with it… and she was behind him.
The next night, Dipper and Mabel crept into their parent's bedroom. Their parents were to leave the next day to go on their ski trip; Grandpa Shermy had already arrived, and was asleep downstairs.
"Are you sure you wanna go through with this?" Dipper asked his sister, keeping his voice down to a whisper as to not wake their mother and father.
Mabel took one last look at their sleeping parents. They were like strangers to her now… she'd seen so little of them since she and her brother had come home. A rift had grown between them, and Mabel couldn't help but wonder if… maybe their parents were tired of them? Was that why they really sent them away to Gravity Falls in the first place? Did they no longer love them?
It hurt to think that this might be so… but at the same time, Mabel couldn't but think that there were people in Gravity Falls who did love them. Stan loved them. Ford loved them.
Mabel had made up her mind. She looked her twin brother in the eye… and nodded.
Dipper twiddled the dial on the side of the memory gun, inputting the words "DIPPER AND MABEL"; he then pointed it at their sleeping parents, took a deep breath… and pulled the trigger.
A flash of blue light illuminated the bedroom, then rapidly faded. Neither Mr. nor Mrs. Pines reacted. They slept on, none the wiser to the fact that their children had just erased their memories… but then, when they woke up, they wouldn't remember even having children in the first place.
Dipper and Mabel were already packed. They'd stripped their bedroom of all their possessions, taking whatever they couldn't live without, and throwing away anything else. Mabel stole money from their mother's purse and used it buy them bus tickets, while Dipper- using a laptop he'd gotten from Wendy as a late birthday present- hacked into their school's computer system, copied all of their records on him and his sister, then deleted the originals.
"What about everyone in school?" Mabel asked her brother as they left the house, bags slung over their shoulders. "They'll figure out what we did, eventually!"
"Don't worry," said Dipper. "I have a plan."
There was cell phone tower not far from where they lived. Dipper was going to use the same trick Ford had used to stop those government agents.
Upon reaching the tower, Mabel located a toolbox with a crowbar inside, and used it to pry open the control box. Dipper wired the memory gun to the tower; come sunrise, no one would ever remember that two children named Dipper and Mabel Pines had ever lived in Piedmont.
"Plug your ears!" Dipper shouted. The gun fired, it's signal amplified by the cell tower, sending a wave of blue light across of Piedmont. Most people slept soundly, but a few were startled awake by the signal, waking up confused in the middle of the night… only to wonder for a moment what had woken them up before falling back to sleep.
Their work was done. Dipper ejected the canister from the memory gun, stuffing it in his backpack along with the gun itself; he'd probably throw it away when they got to Gravity Falls, but he wanted to hear what Grunkle Stan thought of all this, first.
From the cell tower, they ran to the bus station, arriving just in time; the bus was pulling up just as they came to a halt in front of the terminal, panting from having run so far. They climbed aboard, not even stopping to look back at their hometown as they did so. There was no one else on board. Dipper and Mabel took the back seat, along with Waddles; thankfully, the bus driver didn't raise too much of a fuss about letting an animal on board. The doors closed, and the bus took off.
Dipper held his twin sister close, adjusting Wendy's hat as the bus sped off towards their final destination. They looked at each other, and smiled.
"We're finally going home," Mabel said to him. Dipper nodded. "We are," he affirmed.
"Didn't Stan and Ford say they were going to explore around the world?" Mabel asked him. "What if they're not there when we get back?"
"Soos and Melody will be there. They'll understand," Dipper reassured. "You're sure you're okay with this, right? We've pretty much already crossed the Point of No Return."
"I know that, Dipper," Mabel replied. "But mom and dad… they left us all alone. We haven't spent any time together since they got back. I keep wondering if they even want us anymore."
"What you said before, in Mabeland?" Mabel reminded him. "You said I didn't have to be afraid… that there was a better way to get through life than living in fantasy- with help from people who care about you."
"But lately… I've felt like you're the only one who cares about me in this town," she confessed to him, her eyes watering. "And our stupid principal decided that we couldn't be in the same class anymore… our parents don't listen to us, they think Grunkle Stan turned us into 'bad seeds'…"
"Everyone who ever really cared about us is in Gravity Falls," Dipper agreed. "That's why we're doing this- so we can be with our friends and family. Our real family."
Dipper glanced nervously towards the front of the bus; they were keeping their voices down, but all the same, he wanted to be sure the bus driver wasn't listening. The last thing the needed was for him to find out they were runaways.
The trip home took several hours. Mabel eventually fell asleep, her head falling on Dipper's shoulder. Dipper lay awake for a while; he was feeling a little paranoid, that maybe they did something wrong, and their parents would somehow notice they were missing and that a police car would stop the bus at any moment, and the cops would force them to go back to Piedmont.
But nothing of the sort happened. The bus crossed the state boarder without incident, and Dipper- feeling exhausted- finally fell asleep next to his sister. The sun began to rise as they neared their destination.
Then, at long last, Dipper and Mabel were awoken by the bus driver announcing over the speaker:
"Next stop; Gravity Falls!"
Dipper awoke just in time to see the familiar site of the old water tower, the words "GRAVITY FALLS" painted on the side in large, black letters. Feeling excited, he shook Mabel awake.
"Mabel, wake up! We're almost there!" He said. Mabel stirred awake just as the bus took a right down Gopher Road, and soon their summer home- the Mystery Shack- appeared in the window.
At last, the bus stopped. Dipper and Mabel grabbed their bags, hopped off the bus, and beheld their true home. The old house was decked out in Christmas lights, and there were a few inches of snow on the ground. Despite the cold outside, the twins each felt a warm feeling in their chests as they stepped up to the door. They'd made it; and Grunkle Stan's car was out front, so that meant he and Ford, their entire family, were there.
Dipper reached up to knock on the door. When it opened, Grunkle Stan was standing in the doorway- he barely had enough time to feel surprised at his niece and nephew suddenly appearing on his doorstep before they through themselves at him.
"Grunkle Stan!" The kids cried out in joy.
"Kids!?" Stan said in surprise.
It took the better part of an hour for Dipper and Mabel to explain to everyone what'd happened, what they'd done. Every one of their closest friends were there to greet them; Stan and Ford, who looked as though they'd just gotten back themselves… Soos and his girlfriend Melody, although not his grandmother (who the learned has passed away recently); Wendy was there too, and especially excited to see Dipper- indeed, she was still wearing Dipper's pine-tree hat. As soon as she saw him, she threw her arms around him and his sister, enveloping them in a fierce bear hug.
After that, everyone sat back and listened to Dipper and Mabel's sad and lonely tale of their life in California. Stan looked particularly irate when they mentioned how Shermy had treated them, and what he said about Stan himself. When Mabel told them all how their parents no longer cared about them, it was actually Ford who put a comforting arm around her as she appeared close to tears.
"So, I guess that means I can't send you back?" Stan asked them when they were done. "If I take you back to California, your parents won't even recognize you, will they."
"Do you honestly want to send us back?" Dipper responded. "Grunkle Stan; life for us has been heck on earth since we left. You're our really family… our mom and dad don't want us anymore, and Grandpa Shermy-"
"Alright, alright, I get it!" Stan said. "Truth be told, I've missed you kids, too."
"We all have," said Wendy, putting her arm around Dipper. They were still wearing each other's hats. "Things just haven't been the same around here since you guys left."
"So we can stay?" Mabel asked.
"What else am I gonna do? Put you in foster care? Throw you out on the streets?" Stan replied. He just had to be sarcastic…
"You dudes belong here, with us," Soos chimed in. "You're part of our family."
"Speaking of which, when's the wedding?" Mabel asked, eyeing Soos and Melody, who blushed.
And that was that. Stan allowed Dipper and Mabel to move back into their attic bedroom. Later, they went downstairs to catch up with Wendy and Soos, and Ford showed them the new journal he'd been writing; it was like the others, except it was blue with a silver hand and a number "4" on the cover. Ford had already filled it with a compilation of all the research he'd otherwise lost in the old journals, plus some of his findings from his adventures around the world with Stan.
No one would come looking for them in the days to come. Dipper checked the news once or twice to make sure their were no missing person bulletins out for them, while Stan was sure to keep an eye out for the twin's faces on milk cartons, but they needn't have worried.
That year, they spent their first Christmas together as a family in Gravity Falls. Mabel, who'd given up her old hobby of knitting sweaters in depression months ago, returned to it almost immediately to knit some new holiday sweaters for all of them. They went sledding out in the woods, had a snowball fight out front, and Wendy and Melody cooked the whole family a big Christmas dinner. The rest of Wendy's family was still doing apocalypse training that year… but since Wendy was the only one who hadn't been turned to stone by Bill, she was allowed to spend the holidays with her friends.
It was perfect. After nearly four months of loneliness and misery, Mabel and Dipper Pines were finally happy, surrounded by everyone who truly loved them and cared about them, in the place that had transformed all their lives for the better.
At long last, they had found their way home.