The Mystery Shack had closed for the evening. Soos and Wendy had gone home, and Stan fell asleep in front of the television. For the Pines twins this was just the start of another fun-filled night.

With grappling hook in one hand and a piece of caramel in the other, Mabel lured her pet pig into the shop. "Alright, Agent Waddles. This is the mission we've trained our whole lives for. We must stop the evil Dr. Dip from taking over the whole entire world!" She shot the grappling hook at the ceiling and swung to the other side of the room. "Here it is! The secret vault that holds Dr. Dip's evil, dastardly plans is beyond that door!"

"Not so fast!" Mabel and Waddle turned around to see Dipper emerge from behind the counter. "You cannot stop my plans! You cannot even escape! Behold! There's a trap door beneath you!" He pressed a button on the invisible remote control in his hand, but not before Mabel shot up at the ceiling once more, suspending herself above the unseen trap.

"Waddles!" she warned her pet pig. "Don't fall into the trap door!"

"But the whole floor is a trap door," Dipper claimed.

"No fair! Waddles doesn't stand a chance unless…" She squealed at the thought. "Waddles has a jetpack and he's flying above the pit!"

"Nice! Uh, I mean, curses! You survived my death trap! But just try to make it into the next room, Agent Mabel!" Dipper let out the best evil laugh he could muster, but had a coughing fit soon after.

"You'll eat those words, Dr. Dip! And wash them down with Pitt!" She turned to face the vending machine. "This passcode will open the door to the next room. Beep! Bop! Boop!" she blipped as she pressed random buttons on the machine.

"No!" Dipper bellowed. "You cannot escape! I will not have it! I… Mabel, you can stop now," he said, breaking character. "I don't think Dr. Dip would have a passcode that long. Just go in the next room."

"Oh, please!" Mabel giggled. "Do you really think Agent Mabel is going to get the passcode right on her first try? I'm just being realistic!"

"Since when is a secret agent pig with a jetpack realistic?" Dipper questioned.

"Since I said so. Now shut up; I'm trying to concentrate. Beep! Boop! Bop! Boop! Bop!"

Dipper sighed. "Alright, let me know when you open the door. I'm not sure what to do anymore for this part." He turned around, waiting for his sister's beeps to cease. What he didn't expect was the strange hissing sound that filled his ears when her bops stopped. Turning back, he saw, to his bewilderment, a light shining from a now ajar secret passage.

Mabel was just as surprised as her brother. "Whoa! Is this part of the game? What menacing plot have you cooked up for us, Dr. Dip?"

"Plot? Are you crazy? I never even knew it existed! Ma-Mabel!" His sister had maneuvered her way around vending machine. "What are you doing? We don't know what's down there!" He followed her into the secret passage, leaving it open.

"Whoa!" Unlike her brother, Mabel was quite excited about this new secret area they had stumbled upon. Dipper on the other hand was very concerned. Despite all of the creeps and creatures they had brushed up against throughout their stay in Gravity Falls, not once did he expect to find a secret den underneath the Mystery Shack.

There were documents littered all over the place, but nothing that took the fancies of the twins. Mabel was simply in awe at this newfound room, and Dipper felt that there had to be something specific—something of major importance that was hidden here for a reason. He assumed that his great uncle, being the conniving Man of Mystery himself, wouldn't just keep anything in a secret area without trying to make a quick buck out of it. It had to be huge.

His eyes fixed onto a portrait of a middle-aged woman on the far end of the room. Underneath it was a large book resting facedown. His suspicions were verified when he turned it over.

Excited, he called Mabel over. "Look what I found!"

Mabel walked up to him and noticed the portrait. "She's so pretty!"

"No, this." He handed her the book. On the cover sat a six-fingered hand with the number "1" slapped on it.

Mabel gasped. "Dipper! This is just like that other book you have!"

"And the one Gideon has," Dipper pointed out, recalling their past scuffles with the phony psychic. Unfortunately the second book was still in Gideon's possession.

"Well read it, bro!" She gave the book back to him. "You've wanted to find this book for, like, ever!"

"Right." He opened up to the first page. "'Property of Stanford Pines.'" That was no surprise to him anymore, but he noticed that the original owner's name was scribbled out. "So much for finding out who wrote this." He looked at the next page. "Hey, there's a note. 'To whom it may concern, if you're reading this there is no going back. Gravity Falls has sucked you in, and you will spend the rest of your life uncovering these secrets. I should know, because'—what?"

"What's wrong?" Mabel asked, glancing at the note. "'I should know, because I'm you.' Yeah, you're right. That is kinda weird."

"Maybe he means that he had the same love for mysteries as we do," Dipper suggested before continuing. "'I cannot finish what I have started. I have become bitter, having lost the only person in this world that truly understood me. Using the secrets that I have uncovered about this town, I shall pass my knowledge down to the next generation in the hopes that they solve the mystery that I couldn't solve.'"

"That's so sad," Mabel interrupted sorrowfully.

"'I am not sure why I am doing this. Perhaps it is because I went through the same trials, and I'm merely working to make sure the time loop stays stable. That does not give me much hope in finding my sister, but perhaps—in a way—I can relive those days. Too bad it just won't be the same. I am too far gone to appreciate it. At least now I understand why he did it before me.' Who's he?" Mabel just shrugged, and Dipper continued. "'Maybe with the next generation the loop will be broken. I'm afraid of what may happen to me when that happens, but perhaps it will give me some peace of mind knowing I was the one who saved Mab'—" Dipper stared at that word for a moment. This couldn't be what he had in mind.

"Dipper?"

No, it had to be a coincidence. Dipper shook some sense into his head. "'Mabel.'"

"Hey, that's my name!"

Dipper was afraid to continue. Seeing his sister's name wasn't what bothered him, but the fact that this note mentioned a time loop along with it. It just made it all the more possible that what he had in his mind was true, and he didn't want that to be the case. Reluctantly, he pressed onward. He needed to see if his suspicions were true. "'In either case, I ask the next generation to let it all sink in. Do not take for granted what you will most likely lose. When she goes, you will follow. You will never be the same. Good luck, Dipper Pines.'"

Dipper took a huge breath as silence surrounded him. It was too much to take in. What was going to happen to him? And worse yet, what was going to happen to Mabel? Worried for his sister, he turned to her direction, only to find she wasn't there.

Panicking, he ran back to the stairs. "Mabel!" he cried, heart pounding in horror. Whatever happened to Mabel, it couldn't possibly happen this soon.

Upon returning to the shop, he screamed louder. "Mabel! Can you hear me?"

"I can hear you loud and clear, bro!"

He turned to find Mabel in the corner holding up her pig.

"I had to get Waddles. He was probably lonely up here by himself." She nuzzled the pig affectionately. "Who's a good Waddles? You are!"

Dipper collapsed on the floor, letting out a sigh of relief. "Please don't do that again."

"What's wrong?"

"I'll tell you what's wrong," the gravelly voice of Stan Pines filled the room as he entered the shop. "Your brother is screaming his head off like a wild gorilla! Some of us are trying to—AAH!" He had noticed the open passage. His secret was revealed far sooner than he expected it to be. "So, today's the big day. Great! It's not like I wasn't prepared or anything, oh no."

"What happened?" Mabel asked. It was apparent to her that she left at a bad time, and she was kicking herself for it. Literally. "Ow."

"Don't you worry about it, Mabel, hun." Stan waved her toward the door. "Go to bed. I need to have a chat with your brother."

Dejected but understanding, Mabel did what she was told.

When she was out of the room, Stan motioned for Dipper to follow him back into the secret den. "I'm not sure how to explain this. To be honest, I don't remember much from when I was your age. I remember some things; the books, some of the really bizarre stuff, and Mabel, but ever since the incident I've been finding myself getting less and less attached to everything. Perhaps it's better that way, but it's a shame that someone with the moxie that you have is going to, you know, end up like this. And don't try to tell me that you didn't think of that."

"I didn't," Dipper assured him. "I'm more worried about Mabel."

"Well you'll think about it later. Trust me." He took off his fez hat and pointed at his rather uninteresting forehead. "In case you're curious, I got it removed. If I was going to go back in time and pose as my own long lost great uncle, I couldn't have a telltale sign on me. Unfortunately it was botched, and you can still see a really, really faint scar there if you get up real close. That's why I started wearing the fez pretty much anytime I went in public. Now I'm just used to it."

"I don't care about the birthmark!" Dipper was getting annoyed. "What happened to Mabel? You have to tell me so I can prevent it!"

"Kid, there's nothing you can really do about it," Stan hit hard. "I don't even remember it that well anymore, but I know that the power was out of my hands. It would take an anomaly in the timeline to save her, and I could never figure out what that anomaly could be. And believe me, I tried everything."

Defeated, Dipper's eyes began focusing on his shoes. "Can you at least tell me how old we'll be when it happens? So I can be prepared?"

"Trust me, that's not gonna do you any good." Stan pointed back to the shop. "Take my advice, kid. Don't take your sister for granted. Appreciate every moment. Thinking too much about the future is only going to get in the way of the time you have now. It sucks, I know, but that's just what you gotta do. That's life, kid. That's life in a nutshell. Tell you what, though." Stan gave his younger self a genuine smile. "I'm still kickin'. And I still will be for quite some time, if my Grunkle Stan was any indication of that. And I never knew if he found her. For all I know, everything turned out just fine. Gives you something to look forward to, doesn't it?"

"I guess so."

"Good!" Stan gave the young Dipper a noogie in an attempt to cheer him up. "Now go to bed, and try not to think about it so much, okay? Remember what I told ya."

After ushering the sad but hopeful boy up the stairs and trusting him to head for his room, Stan walked back to the book to shut it. Looking up at the portrait, he sighed once more. "Things aren't looking good for either of us, huh, Mabel? But we sure had fun though, right?" He nodded to himself. "Yeah. Yeah, we had fun."

-X-

Author's Note: I posted this on DeviantART, and I figured I should post it here as well. I have another one I'll be uploading shortly.

This is based on two popular predictions on where Gravity Falls is going: Stan having Book 1 (which I totally agree with) and Stan being an older Dipper (which I'm not so sure about but I love the idea regardless).

As usual, I don't own a darn thing.