"Come to the forest tonight."

"Why should I?"

"I know you, pine tree." The weight behind the words sent a shiver through Dipper—Bill said them with a smug sincerity that Dipper knew was justified. "You can't leave a mystery unsolved."

It was true.

After high school, Dipper had moved out to Gravity Falls for good. He told his family he was going to keep Stan company, and learn more about the business so he could take over some day. It was true Dipper loved the old man and the Mystery Shack, and the town had its share of charm...but there was something that drew him back more than nostalgia, old friends, or Stan.

Over the years, Dipper and his sister had returned to Gravity Falls every summer, and every time uncovered more secrets, solved more mysteries—but there was one thing Dipper could never figure out. Bill Cipher. It was as if something blocked him at every turn, blurring the connections that would give him his answers. The more frustrating and unsolvable it became, the more it consumed Dipper. Even when he left Gravity Falls, thoughts of Bill never left his mind for long. It had turned into an obsession.

He knew Bill was watching him. At first it was a passing glance—after all, wasn't Bill watching them all? Bill had no reason to give him much more thought than the others. But as Dipper dug deeper, things began to change. The demon had to intervene in the growing boy's mind, had to pay him more attention—he was turning into an interesting opponent, if not a bit of a challenge. The harder Dipper fought, the more Bill taunted him, and the closer he watched. It was an ominous feeling, but Dipper had gotten used to it, and now considered it all part of their little game: anywhere he went, Bill would be watching. Sometimes, when no one was around, Dipper even spoke aloud to him. Bill became a constant in his life.

The first time Bill had slipped into the boy's fantasies, Dipper tried to tell himself that Bill was messing with his mind, tormenting him. The truth was Bill himself played no part—Dipper's mind was working independently. The demon was intrigued, though—perhaps when the boy was older he would prove more fascinating than Bill had anticipated.

As Dipper grew up, so did his obsession, and he slowly lost interest in girls, and then interest in anyone. He was back in Gravity Falls, a young man now, and Bill was now participating in his fantasies, making them real. Dipper knew it was sick, but it was perfect.

There was a small community college nearby, where Mabel studied art and design. Dipper had dropped out. He had other things on his mind. When he wasn't working for Stan or with Mabel, he spent most of his time in his room, or out in the woods...and following Bill's instruction, it was the woods he had come to tonight.

The sun was over the horizon, but the summer heat lingered as the light diminished. Dipper enjoyed the soft crunch of his sneakers through the dry forest trail and the last quiet bird songs of the evening. Despite everything weird that happened there, or perhaps because of it, Gravity Falls was a beautiful place.

"Hello Bill," he said quietly.

"Well well, Dipper Pines. I'm surprised at you." The demon floated nonchalantly around Dipper to face him, giving him a look over. "I thought you might dress for the occasion."

Dipper swatted away Bill's cane, which was poking disapprovingly at his casual light jacket. "Occasion?"

"Don't tell me you forgot! It was ten years ago today you first met me, kid. You might say it's our anniversary!" He floated away slowly as he spoke, straightening his bowtie as if to spruce himself up for the human. His eye was closed, and if he had a mouth, Dipper was sure he'd be grinning. It was that attitude that drove Dipper nuts. Bill was a trickster, and a bit of a dork—he had no right being that charming, and Dipper felt like a sucker every time it worked.

"That's why you brought me out here? Shoulda guessed it'd be something ridiculous." Dipper folded his arms and tried to sound unimpressed.

"Ah don't be that way pine tree, or you won't get your present," said Bill.

Dipper melted a little when Bill used the nickname, which seemed to have become an almost affectionate term. "Alright Bill, what is it? Deer teeth? Woodpecker feathers? If it came out of an animal, I don't want it." He was mostly teasing—they'd been over this for real before, and he was pretty sure Bill got the idea.

Bill's laughter rang through the forest, and echoed around Dipper's head. The world around them seemed to suddenly slow and fade. "No pine tree, a real present this time. Y'know you're pretty easy to shop for! What's the one thing you want most? The same thing you've wanted for the last ten years—answers!" He threw his little hands up in the air with excitement.

Answers? Really? The young man's insatiable curiosity was definitely piqued, but this had to be a trick.

"No tricks, Dipper, I'll give you all the info you want." Dipper wasn't phased, he was used to Bill answering thoughts he hadn't voiced.

"Okay then, let's have it," agreed Dipper. He was still skeptical, but his skin was tingling.

"But what about my present? Don't be greedy."

Ah, so that was Bill's game. Still, if he was actually willing to negotiate a price, Dipper would listen. After all these years, there was very little he wouldn't give to solve the mystery of Bill Cipher. He wanted to know, he wanted to know everything...and he'd be lying to say he didn't love every moment of this.

Dipper's desire was intoxicating to Bill. He actually wanted to play! What a wonderful human. He saw words on Dipper's lips and silenced them by floating close and staring into his eyes, into his mind. Dipper felt the demon's answer to the question he hadn't yet asked echo in his head as the world around them went black.

JUST PROMISE TO BE MINE

Dipper hardly considered it a price at all.