AN: Hey! Just wanted to pop in quick to dedicate this story to an awesome user on this site, sapphireswimming, to celebrate her 100th fanfic! This story is based upon her lovely 100th fic, "Down the Road" in the SuperPhantom crossover category.

A quick point about this story. It doesn't feature any of the characters from Supernatural but I put it here in the crossovers section because the lore and references are clearly from the show (also "Down the Road" is a SPN crossover) as well as because I tried to write the boys in and wish they were there.

Enjoy!

The first time Dipper opened the journal after leaving Gravity Falls was when he heard the barking.

In the nine and a half years since that fateful summer in Gravity Falls, neither of the Pines twins had encountered anything remotely supernatural. That didn't mean they hadn't looked: at first it was to see if any of the incredible things they had encountered that summer existed outside Gravity Falls, then it was to pass the time while they waited to go return to the Mystery Shack in June. The next summer, when they realized that Grunkle Stan refused to invite them back, citing some con of an excuse that clearly translated to Dipper and Mabel as "it's too dangerous for you here", the twins dove headfirst into the treasure trove of supernatural lore on the internet, trying to find something, anything, that could prove to Grunkle Stan that they were more than ready to handle what Gravity Falls had in store.

But the more they searched, using their own personal experience to weed out the fantasy from the truth, the darker the lore became. It was after reading three accounts of young girls vanishing into a forest in Maryland after claiming that their short, beardy, but otherwise normal boyfriends, were actually gnomes that Mabel first went into Sweater Town. Over and over the twins would read tales similar to theirs, involving ghosts, vampires, zombies, even pixies like the one Soos accidently swatted against the Shack window, killing innocent young children to the most paranoid veterans of war.

One night in the middle of winter Mabel decided she couldn't take it anymore, that she would rather talk to Grenda and Candy on the phone instead of seeing them in person if it meant not having to deal with the creatures that haunted Gravity Falls. Mabel had hoped that her little (if only by five minutes) brother would quit, but Dipper remained as obsessed as ever, often working late into the night on his laptop looking up encounters with various creatures and how to kill them.

One time he even went so far as to ask their parents at the dinner table if they could drive down to Jericho to investigate a murder mystery. Their parents, having heard tales of Dipper trying to find who cut the head off of wax Stan and thinking it was just some touristy mystery dinner show, laughed and told him that the fourteen hour drive to Jericho was too far and he would have to wait until he was older solve actual murders. They were proud their son had such drive to become a detective, but when Mabel saw the corkboard filled with newspaper clippings of various murders Dipper claimed to be caused by a "Woman in White", she knew her brother was going down the path Grunkle Stan tried to steer them off of.

The last time Dipper even thought about the supernatural was that evening when he looked up from his latest breakthrough in his research on the true nature of werewolves – maybe he should send this to Soos to deal with the mailman – only to see Mabel curled up on her bed across the room (they had never shared a room until their summer in Gravity Falls, but one part of that summer that would never end were the nightly sleepovers), her eyes watching him forlornly, her legs curled up in an upright fetal position and tucked inside the fuzzy shield of her sweater. Dipper sighed and closed the laptop, not even bothering to save his files before pattering across the shag carpet and jumping up on the bed next to his sister.

"Come on Mabel, there's no need to hide out in Sweater Town. What's wrong?" A series of marbled grunts came out of the sweater until Mabel paused and with a jerk popped her lips above the turtleneck of her purple sweater, the one with the shooting star on it, propping her head in a way that gave Dipper the impression she very much would like to keep her head buried in the sweater if she was able to talk around it.

"I don't like it when you stay up all night looking at that supernatural stuff, bro-bro." Dipper looked over at his sister in shock. He thought at first that something went wrong with Grenda and Candy, or maybe that she broke up with yet another boyfriend at school, but he never imagined that Mabel would wind up in Sweater Town over him. "You haven't gotten any sleep this week, you haven't talked to me about something that isn't a monster in three days, and you're starting to remind me of the time with the laptop and Bill and the sock puppets and you're not Bipper but I want my brosef back!"

The last punch knocked Dipper into silence, figuratively and literally. Mabel had unwound her arms from within her sweater and punched at him, the purple yarn-clad fist hitting him in the side and pushing him against the wall. It wasn't that Mabel intended to hurt him, though the glittery girl always packed more of a punch than most would expect, it was that Dipper just remembered that he hadn't been eating or sleeping and what should've been just a hard tap actually started to hurt. As he leaned back in to hug Mabel he remembered how much this was like the fateful car ride back from the puppet show, and realized that yet again his obsession with the paranormal almost cost him his sister.

"I'm sorry Mabel, I guess you're right. I do have a tendency to get in over my head when it comes with the mystery stuff," Dipper tried to laugh the statement off, but his awkward chuckles died down at a deadpan glare from his fluff pile of a twin. "I'll try not to go out looking for anything dangerous… honestly this time, not like when we were trying to get Grunkle Stan off our backs!" He corrected himself quickly there, and sighed in relief when he saw the hands Mabel had been raising into her "skepticles" position slowly lower back into the sweater.

"Besides, anything we do we do together, right Mystery Twin?" At this he finally saw a smile growing on his sister's face, her right hand finally popping out of the end of her sleeve in order to pound the fist he left waiting in the air.

"Mystery Twins." She smiled. Then paused. "Wait, how do I know you won't just start doing more research when I'm sleeping?"

Dipper's face lifted into that sheepish grin she always laughed at, the one he usually only made if he was caught thinking about Wendy at an inappropriate time, before settling back into a comically serious look as he made up his mind. "I promise, no more looking into any supernatural. If we go on anymore paranormal adventures, the mysteries will have to find us. I won't go sticking my nose too far in if it makes you unhappy." He pulled his fist, still resting against hers, back an inch an opened it into a hand. "Deal?" The sheepish look was back, before he tried to pull his face into one of the crazy expressions Bill made when running around in his body. To Mabel, Dipper just looked like he was constipated.

"Deal!" She laughed as her hand reached forward to shake his, bouncing up and down twice to seal the promise. They both had enough respect for what had happened that day that she knew Dipper wouldn't go back on his word; that was one of the things that separated that monstrous triangle from her brother.

They both smiled for a second as they met each other's eyes, Sweater Town all but forgotten, until Mabel broke the moment by lunging forward screaming, "BODY SPASMS!" and tickling Dipper until his screams caused their parents to yell up asking the twins to be quiet.

Dipper had kept his bargain with Mabel until he was twenty two, curled up on his bed in his apartment, staring at the journal on his lap with wide eyes as the howls only he could hear continued to rage on in the background. That promise was one of the most precious things shared in a long line of secrets and inside jokes that kept the Mystery Twins closer than most others could comprehend, each having given up their chances at the best colleges and art schools in the country to go to college together at a school where they could each follow their passions, then moving into a shared apartment after graduation so Dipper could find work as a PI while Mabel sold her artwork online. Life was going great free from the supernatural and paranoia that followed that journal and everything from Gravity Falls, and Dipper didn't want to cast Mabel aside and dive back into the world of the unknown but he couldn't live ignoring the puffs of breath being blown in his ears or the chills crawling down his spine and he knew the fastest way to get to the truth would be to consult the author.

A strong gust of wind blew through what Dipper could have sworn had been a closed window and pushed the cover open in front of him, seemingly taunting him with the possibility of answers before settling on a page that Dipper knew all too well. Although he no longer had every page of the book memorized Dipper knew he would never forget the letters and symbols drawn out on that page in red blood (how had he once not noticed what that was) and black ink. The three sided body and singular eye of Bill Cipher – Demon! – stared unblinkingly up at Dipper before he slammed the cursed book closed, the thud of the cover slamming on the paged accentuated with a loud bark from just outside the apartment that made Dipper jump in his place.

He gazed hopelessly down at the book in front of him, his mind reasoning that he had already broken his promise to Mabel, albeit unintentionally, and there was no way he could hope to apologize without getting her involved, and hadn't his promise been that the mystery would have to find him, and it certainly already had – before he realized that he just had to damn himself and opened up the cover one final time. His hands shook as they frantically turned through the pages, his eyes trying to read or recall anything that could do with dogs, barking, monsters that only their victim could hear because he knew that if he didn't do anything fast they were going to come for him before they all too quickly found the end of the notebook and started turning the other way again.

Dipper vainly tried to remember if there was anything related to dogs hidden in the Author's notes only visible with blacklight, but Dipper cursed and panicked even more as he realized that the blacklight he had was back in Piedmont because why would he ever need one if he was done with mysteries, he only brought the journal out of sentiment. He hadn't even realized his hands had stopped moving when he looked down and saw the journal open to the one, all too familiar page that he never wanted to see again. But this time it looked different, and Dipper found himself unable to even register the growling that was growing louder and closer as the drops of blood splattered on the page began to bleed anew, seeping and trailing on the page into perfectly detailed drawings of an arm with forks in it, a wedding cake with a dead bride in a pink sweater on top, and Wendy, with her long, blood-red hair flowing seamlessly into the trail of blood left by an axe in Dipper's hand, the shapeshifter howling triumphantly before escaping out into the real world.

Dipper blinked subconsciously as his eyes began to blur from half-formed tears, the terrifying images thankfully vanishing as his eyes searched the page anew. His hands clawed at the text, leaving tears at the edge of the paper, until a single teardrop fell from his eye and landed on the black shape in the middle, bolded at the center of the page, and soaked right through Bill's right hand. The figure remained unchanged but Dipper's breath sped up again, his heart skipping a beat as it moved back into overtime, as from the edge of the new stain a blue flame appeared to engulf Bill's hand before Dipper's very eyes.

The static inside Dipper's mind seemed to escape into reality as he dropped the journal and screamed, pushing himself back into the wall as the howls rose to the forefront of his thoughts. He might have been in Dipper's imagination, but he could have sworn that the tan walls of his apartment were drained of all color, yet as the T.V. set that Dipper knew was off just a minute ago changed from static to the eleven o clock news, everything seemed to be in perfect color. Shandra Jimenez seemed to be as stoic as usual as she announced the top story, psychic and child star Gideon Gleeful found dead in his home, his body torn to shreds by what the medical examiners disbelievingly noted appeared to be a pack of wild dogs, the cameras showing the gruesome crime scene, void of a body but filled with far too much blood and a battered journal laying on the floor, its spine bent at an unnatural angle, appearing to be the only thing left that wasn't newly painted red. For just a split second before the T.V. flickered off Dipper could've sworn he saw the book consumed by the same blue fire that had burned the page in Journal Three, that signified Bill, that signified the deal that Dipper made with the devil and the deal that Dipper broke with his sister and the life that Dipper got too deep into despite everyone's best intentions, and Dipper didn't have to be psychic to know that he wasn't getting out alive, that no one who got burned by that fire and dragged into the life ever did.

And despite the barks and howls screaming in Dipper's ears and out of his own throat the mystery hunter was able to clearly make out the demon's taunting words.

"Tick-tock kid."