The Gravity Falls fandom needs more Stan & Dipper stories about their relationship. Also I now have terrible case of the feels after Not What He Seems and these two stubborn idiots give me life (and much heartache), so here's a plot bunny I've had for a couple of months now.

Disclaimer: I don't own Gravity Falls, just the plot of this fanfic and any OC monsters. This is set after Sock Opera.

Whispers in the Dark

Ch. 1

"You're doing what?"

Mabel rolled her eyes from where she laid on her bed, sticking out her tongue in the general direction of her sibling. "Dipper, it's just a sleepover at Grenda's house. It's just one night. It's not like I haven't gone before."

Her brother sighed and flopped onto his back on his bed across the attic. "I know, it's just...I wanted to explore these caves I found with the blacklight yesterday. You know Grunkle Stan is getting suspicious about the whole supernatural thing, promising to stay out of trouble and whatnot; he won't like it if I ask to go out into the forest alone with the journal."

"You could bring Waddles, if you want," Mabel said half-jokingly. "Grenda's mom doesn't like having 'messy animals' in the house. But of course, a pet lizard that sheds is alright..."

Dipper groaned and draped an arm over his face as his sister grumbled under her breath. It wasn't that big of a deal, honestly. Mabel had slept over at her friends' houses at least four times already, and the amount of times she'd invited Candy and Grenda over here were numerous. The preteen wasn't worried about what would happen at the sleepover or anything, he knew Mabel could definitely take care of herself if the need arose. It was just that he had really looked forward to exploring those caves with his twin today. But instead it had rained until three o'clock and Stan wouldn't let them out because of how badly it was pouring, and now Mabel sprung the whole sleepover surprise on him...

"Are you sure exploring is the real reason why you're all grumpy, Dippingsauce?"

"Huh?" Her words jerked him out of his slump as he struggled to process them. He sat up, removing the arm from where it rested on his face. "What's that supposed to mean?"

Mabel stopped stuffing her nightgown into the suitcase and shot him a startlingly serious glare. "Don't play dumb, bro-bro. I'm talking about those dreams."

Oh.

He had hoped she had forgotten about those. Then again, it had been over a week since that day, and they hadn't gone away.

"Mabel, that's not the reason why I'm upset."

"Uh-huh, sure."

"Really!"

His twin rolled her eyes, but she set down the clothing in her hands and walked over to where he was sitting. It was a strange sight to see the usually energetic girl still and serious.

"You'll be okay, right?"

Dipper's lips twitched slightly despite his twin's nervous tone. "Yeah, of course, Mabel. I can handle a few nightmares."

Mabel shot him another glare. He noted that she was starting to wring her hands anxiously. "I'm serious, Dipper. I know you're still having them, even if they're not as bad anymore. If... If you want me to stay instead of going - "

"What - ? No, no! Mabel, it's okay!" He scooted closer to grab her hands so she'd stop twisting them about. Her nervous antics were starting to make him feel antsy. "I'll be fine, really. You don't have to stay and cancel your plans just because I'm having problems. Besides, you've been stuck with me for over a week now. I think Doctor Mabel needs some time off."

Her eyes seemed a little watery, which momentarily scared the boy before she blinked it away and embraced him tightly. He couldn't help but hug her back, fisting his hands in her purple sweater.

"I just... after what happened... you know I worry about you too, right? I just don't want you to think I'm abandoning you or anything - "

"Mabel," Dipper cut in gently, ignoring the way his heart ached at her words. "You're not abandoning me. You're going to Grenda's house, and that is okay. I know you're worried, but I'll be okay without you for one night. It's just like every other sleepover, right?"

She sniffed and nodded against his shoulder. "Right."

Mabel peeled herself off of her brother, wiping furiously at her left eye as he offered her a small smile. She managed to give him a weak glare.

"You'd better call me if you have a nightmare, okay, Dippingsauce? Or even talk to Grunkle Stan about them if you can't get to a phone."

Dipper snorted at that idea. Talking to his great-uncle about something like this was impossible. Sure, the old man knew about the supernatural and Dipper knew now that he didn't hate him, but having a conversation about the nightmares... No, that just wouldn't happen. Plus, it would mean admitting that he had broken his promise and he didn't want to know how Stan would react to such a thing.

"Yeah, I'll call you. I promise."

Mabel shot him a knowing look. "Grunkle Stan could probably help too, you know."

He snorted again. "Yeah, that's not happening. It would be too awkward for the both of us, and then he'd get mad because... well, that would mean admitting everything we've done since the zombie incident!"

His sister huffed in exasperation and said, "He worried about you too, Dip. If he knows anything about what's going on, maybe he could help. I'm not saying you have to... it's just a thought."

"Look, Mabel - "

"Will you at least think about it? For me?"

No, she wasn't going to use the puppy dog eyes on him. No, that wasn't going to work, it wasn't, dang it - "Alright, I'll think about it."

Mabel smiled wide. "Promise?"

"Promise."

"Good!" She hugged Dipper tightly once more and he chuckled at her renewed enthusiasm. "Don't worry, Dipper! I'll be back tomorrow before lunch, and then the Mystery Twins are back in action!"

Dipper rolled his eyes playfully, something odd shifting in his gut. Waiting so long to explore after being fussed over and not leaving the Mystery Shack for a week... he could stand to wait a little bit longer, right?

His gaze flitted over to where the journal lay open by the window. Of course he could. He could wait for Mabel.

He could survive one more night.

DSRHKVIH RM GSV WZIP

If there was one thing Stanford Pines was known for, it wasn't being a patient man. He often couldn't stand grocery lines because they moved too dang slow, or even gritting his teeth every time a customer took more than half an hour in the gift shop to decide what to spend their money on. He had no patience for slow folk or those who liked to take their time to be perfectionists in everything they did.

It was funny how that logic was being completely disregarded now after thirty years of searching and playing his cards right - and being patient, of all things.

His brother would have been proud, Stan thought a little bitterly as he typed in a few coordinates in the computer. Mabel was off at some sleepover and Dipper had gone to bed around nine, saying something about being tired or whatever. It was fine by him, as long as the kid wasn't doing something detrimental to his health, because it meant more time to work on the machine.

His fingers paused mid-sequence as that thought replayed itself in his head. Ever since the strange accident at the older girl's sock opera, Dipper had been acting a little odd (odder than usual, which was saying something considering how often the boy would go off on tangents about the weirdness in the town). His dark bags had begun to fade away but the tired look in his brown eyes hadn't. The cuts were healing - yet every time he actually dared to ask Mabel about how her twin was (not that he was worrying about Dipper, no, why would you ask such a thing, was it getting hot in here or was it just him, heh?) the girl would give him a thin smile that told him things were definitely not okay.

What was wrong with the kid? He didn't act like his scrapes and bruises were hurting, so maybe it was a mental issue. Neither of the twins had approached him to explain the details of what had gone down that day, why they had been fighting onstage one moment and setting off fireworks into the audience in the next, why Dipper was almost dragged out by his twin who was telling Stan to stop standing there and staring because he needs help, oh my gosh, help me!

Stan sighed heavily and continued typing. He was growing soft because of these two, he just knew it. He'd officially recognized these feelings for what they were by the time he'd been on a pterodactyl's back punching it in the face - Was this really what his life had become? Yeesh, the things he did for these kids - yet every time he thought about them, they seemed to just intensify. It left a weird burning sensation in his heart... not that it wasn't unpleasant or anything.

He wondered how his brother would have handled these two. Dipper and his twin were surprisingly alike, what with all of the stubborn book-loving bones in both of their bodies. Now that he thought about it, Mabel and Stan himself were a little alike too. It was funny, he had never noticed that. Maybe it ran in the family.

A low groan escaped his lips as his eyelids fluttered. God, he was tired. He had spent almost every night down here in the lab and while progress was certainly being made, it wasn't enough. None of it was enough to fix his mistakes.

No, no more guilty feelings, Stan scolded himself, pinching his arm to keep himself awake. There would be time for that later, when he finished all of this.

The kids were going to hate him by summer's end, and he knew it. It was best that he enjoyed this while it lasted.

DSRHKVIH RM GSV WZIP

He couldn't survive one more night.

The preteen boy paced the attic floor, his sock-clad feet barely making a sound as he chewed on his lower lip. In his hands he held a blacklight over the journal, scanning the pages on the mysterious caves he'd so recently found. It was just a peek, no harm done. Stan had gone to bed a couple of hours ago and now it was nearly one in the morning, but he couldn't sleep, not with the anxiety and the curiosity building up inside of him.

Or, in other words, Dipper Pines didn't want to sleep because he knew what would happen once he drifted off.

Mabel didn't need to know. He'd just find some time to sleep before she got back to the Shack, when someone was awake to hear him screaming and gosh, he couldn't sleep with the memories of previous nights dancing in his head.

They hadn't gotten worse, his sister hadn't been wrong about that. The problem was, they had not stopped becoming frightening to the boy, especially when his body occasionally ached in remembrance of not too long ago. It was the same every night, yet even with its predictability he couldn't figure out a way to stop it from occurring.

Maybe he'd look that up in the journal later.

Dipper sat on the edge of his bed after another minute of pacing and rubbed his eyes. He needed something to do, something to keep him awake and occupied. He couldn't fall asleep.

Glancing at the page still lit by the blacklight, he noted that the author had written to the side of an illustration: CAUTION. CAVES ARE VERY NEAR AND DANGEROUS. DEFENSES?

He frowned and scanned the tiny hand-drawn map at the bottom of the page. It appeared to be of the forest and - wait was that the Mystery Shack? His eyes widened. If those caves were nearby and as dangerous as the author seemed to think... No, he had to see for himself. Besides, what was so terrible about it all? There were no monsters inside according to what was written down.

He continued to read below the warning: My studies have brought me to the entrance of this cave and I have heard rumors that perhaps whatever is inside can calm your fears. This would be particularly useful so I consider the possibility an added bonus to my exploration. I will venture inside and write down my research later.

Cure your fears, huh? Dipper bit his lip. That would help him sleep at night. There was no added passage about the discoveries. Did it really work? What had he found? Maybe the caves weren't that dangerous after all.

Curiosity burned in his gut as he shifted his weight on the bed. No, he couldn't.

No...he shouldn't.

...Well, if he was back quick enough...

After all, Stan was a heavy sleeper. He could definitely be back by morning.

But Mabel... she was going to explore with him tomorrow. He should wait.

Dipper groaned and sat there silently for a few minutes, mulling over his options in his head. Another groan and a mumble of something unpleasant left his throat.

He wasn't going to wait. Sorry, Mabel.

DSRHKVIH RM GSV WZIP

Stan rubbed his tired eyes and stood from the chair as code raced across the screen. He should get to bed, it was almost one twenty and he was exhausted already. The machine could wait for tomorrow night.

He watched the last of the code vanish to be processed and after waiting a moment, just to be safe, he shut everything down for the night.

The older man was right about to turn off his surveillance cameras around the Shack when he spotted something in the shadows that made his blood run cold.

Something small was hurrying in the dark towards the woods, turning on a flashlight once at the edge. There was no mistaking the boy's face in the light.

Stan swore loudly and almost ran for the elevator. Idiot! He should have known that that kid wouldn't have kept his promise. After all, it wasn't like he had kept his either. That boy was too curious for his own good, and no matter how many times he had been in those woods, he didn't know how to protect himself from all of those supernatural creatures - especially those ones he didn't know of. Especially at night.

The elevator seemed to be moving at the speed of a snail and when he finally got out, he hurried out of the vending machine, nearly slamming it shut before grabbing his shoes and some clothes other than his boxers and wifebeater. He ran out the door, already out of breath as he took off in the direction the boy had been going.

I should have known you'd do this.

Oh! And by the way...

Mr. Atbash is glad to see you.

Enjoy the rest of the story!