If you play the Mystery Shack game on the disneychannel website it has hints that Gravity Falls actually takes place a few years in the future, so Sophie is the same age as them and Jamie's seventeen. Enjoy!

It was a lazy Sunday afternoons, the ones where the Mystery Shack required no work or effort on their part. The twins laid on their matching beds, tracing the boards of the ceiling with their matching eyes.

"We could go to the arcade…?" Mabel suggested, tearing the thin veil of silence that had covered the room like dust.

"Nah. Just looking at those condoles makes my stomach hurt," he claimed, but he scratched at the eye Rumble McSkirmish had once turned black, "We could go exploring in the woods."

"I've had enough gnome marriage proposals to last a lifetime, Dipping Sauce." She sighed, smacking the lips that had once been suctioned to death by a hormonal-crazed leaf blower.

"We can't mess with Wendy because she's out with Robbie."

"And we can't hang out with Gretchen or Candy because Grunkle Stand scared their parents into hiding."

"You know," he felt the biting cold on his frosted window and gave a shiver, "I think it's too cold outside to really do much of anything."

"Weird. Isn't it supposed to be the middle of summer?"

"Yeah," he slid his fingers across the glass, taking built up condensation with him, "That's what I was thinking."

Mable screamed.

"What?" he looked frantically around for any sort of intruder, "What is it?"

"Snow!" she squealed, charging the window. She began to clap madly, a terribly bright smile threatening to split her face in two,

"Snow! Dipper, it's snowing!"

There were small flakes floating down, few and far between, and if he had just given it a glance he wouldn't have noticed, but his sister grinned and laughed as if it was Christmas.

"Yeah. It is." He smiled the tinsiest bit, but his smile brightened and grew to that of Mabel's stature as the snow began to pick up, glittering, precious snowflakes gently falling. He hesitantly reached out, wanting to touch it, but not trusting it to be real. Mabel grabbed his hand and pressed it to the glass, sensing his desire and acting on it as if a window touch was all he had wanted. They didn't question it anymore, the sharp, intellectual parts of their minds dulled by childlike wonder. In an instant, Dipper was combing through his luggage for a heavy jacket he had told their mom he had no use for. Mabel had tied a gold scarf around her algae-colored sweater and threw on some wool amethyst leggings to go under her navy skirt. They were down the stairs in no time, Mabel almost out the door as she hopped on one foot, tugging her boots on. Then the phone began to ring. Dipper froze as the alarm ran through the shack.

"Come on, Dipper, Grunkle Stan will get it!" It rang on, reverberating through the empty building like ripples in a pond. She stopped hopping, setting her foot down next to the other, barefoot. The phone continued to cry with the urgency of a newborn. Dipper picked up.

"Hello?" he winced and held the phone a bit further from his ear, "Sophie? Soph is that you?" he asked, "One second… Mabel, it's Aunt Rachel's phone she's calling on."

"How did she get this number?"

He shrugged. Outside the snow fell harder.

"Soph, slow down. Who's coming? You and your mom?"

The wind began to twirl madly.

"… Jack? Who's Jack?"

He threw a wary glance at the storm that started to brew outside.

"Frost? Jack Frost? But why? … What about Jamie? Is Jamie alright? … Soph, you're breaking up, there's a snow storm moving in."

He hung up the phone.

The wind was picking up, slamming the front door closed, and then back open again, going back and forth so frequently it looked more like a flag flapping in the wind than anything else. Mabel closed it before the storm could rip it off its hinges.

"So no snow day I take it?"

"Why would Sophie call us?"

Mabel sighed. They had just been denied the first snow day of their lives and he had skipped the mourning process completely, jumping all the way to the pace-around-the-room-and-grab-at-my-hair part.

"Because she's an attention-seeking twelve-year-old?" Mabel tilted her head.

"Hey, we're twelve too —"

"Thought we were thirteen."

"— and plenty attention-seeking. But even we wouldn't do something like this. She mentioned Jack Frost? Do you think that has anything to do with the weather?"

"You think Jack Frost actually exists?"

"Probably not. She might've meant to warn us about the storm, you know she just likes to reference Norse mythology when she talks to us. Like, Rachel made her call us to wish us a Merry Christmas, and she never said Christmas once, it was all 'hey, you guys excited for Santa?' I really don't know when it comes to her anymore."

"Mom told me that Jamie was like that when he was her age. And what exactly do you mean you don't know, you were excited for Santa, right?"

"Well…"

"You do believe in Santa Clause, right, Dipper?"

He fiddled with his thumbs.

Her whole face dropped.

"I can't believe this. You don't believe in Santa Clause? After everything that's happened this summer… you're seriously doubting Santa's existence?"

"I…" he wanted to say it was because he caught Mom putting presents under the tree last year, but stopped because he didn't want to ruin Mabel's fantasy of a jolly man coming in the night, no matter how untrue it may be, "I just don't believe in him anymore. It's time we grew up, don't you think?"

He didn't mean that last part, but it came out anyway.

"Yeah," she said, "Whatever. It is weird that she called us though. How did she get this number? Aunt Rachel's on Dad's side, I doubt she's even met Grunkle Stan. And just to warn us about a little snowstorm…?"

"Well." He said, "Where is Grunkle Stan? He normally comes running when the phone rings. He always thinks it's that one sweepstakes thing he entered six years ago. So he's not here. And…neither is Soos, kinda strange considering he's normally always here. It's just me and you Mabel."

"Alright, so why do you think Sophie called us? Maybe this was a really bad storm everyone knew was coming, so they all boarded themselves up somewhere safe ahead of time. I know he went out last night, so maybe some sort of blizzard warning went off and he had to stay there? I think he might've gone to the diner to see Lazy Susan."

"No," Mabel said distantly, "I don't think it's that."

"Then what do you think?"

"I think maybe this does have something to do with Jack Frost. I mean, think about it. He's like a bitter old man, right?"

"You think he's mad about something?"

She nodded.

"Someone in Gravity Falls made him angry. If we figure out who angered him or why, maybe we can try to make amends and get him to stop attacking us. Think! What would a winter spirit hate? Heat? Summer?"

"Disbelief." Mabel suggested spitefully.

She was probably still mad about the Santa Clause thing.

The door broke at her words, splintering like a toothpick between Manly Dan's fingers. He took her hand, and together they ran down to the basement, slamming the door behind them. The house rattled like a frightened Chihuahua, and they sat huddled in the corner, shivering at the quickly-dropping temperatures.

"O-o-okay," her teeth chattered, "We really have to think of som — Did you hear that?"

"Hear what?"

"Shhh! Listen."

It was the wind. It howled like a wolf sacrificing its voice for the moon, but there was a whining undercurrent, like the cry of a kicked puppy.

J…a…

It whispered.

a…m…i…eeeeeeeeee

"Okay, I definitely heard it say Jamie."

"Didn't Sophie mention Jamie to you?"

"Do you think Jack Frost is really Jamie?"

"I don't know, if you were a Jack Frost, would you be calling your own name?"

"No, but what would he want with Jamie? Besides, he's visiting his girlfriend's college all the way down in Texas."

"But he knows Jamie. So maybe Jamie told him to come here? That could be why Sophie knew."

J—amie.

It didn't sound like the wind anymore, or a wolfish howl. It sounded like the guttural sob of a boy who had just lost his only friend in the world.

Mabel stood up, her one bare foot jolting from the cold of the basement concrete.

"Where do you think you're going?"

"He sounds hurt."

"So you're going to go after a crazy old man with ice powers? No, no, you are staying here." He grabbed on to her sleeve.

"Dipper," she admonished, taking her sleeve back, "You're not scared, are you?"

"No, of course not. I just know the difference between what's safe and what's absolutely insane."

"Well, I'm going." She declared, marching up the steps.

"Wait!" he called, racing to catch up with her.

Mabel froze at the stop step.

"What, what is i—"

There was a boy, who couldn't be older than Jamie himself, curled in on himself on the steps to their attic bedroom. Outside, the storm shook the house, but inside gentle snowflakes floated downward oh so slowly.

He sniffled, and pushed his palm on his eyes, saying Jamie like it was the most woeful name ever conceived.

"Is that…"

The boy jackknifed up, clutching his staff and aiming it threateningly at the twins.

"Are you Jack Frost?"

This took him by surprise. His staff lowered, and his eyes widened.

"Y-yeah. Jack Frost, that's me."

He grinned, but his azure eyes sang a rather melancholy tune.