Dipper and Mabel made their way to the library as quickly as they could that morning. Dipper went to the catalog and managed to track down a book called "Terminal Commands For Dummies." Mabel, of course, teased him about the title.

"Hah! You're a dummy all right, Dipper!"

"You know those titles are only like that to be eye-catching, right?" Dipper said as they went to find a table.

Mabel waved a hand at him. "Ah, that's just what they want you to think!"

"What does that even mean, Mabel?" She just laughed, and Dipper rolled his eyes. They managed to grab the same table that they'd had last week. "Alright, let's try this again, shall we?" Dipper said, turning the laptop on. As the startup graphic loaded, Dipper flipped open the book to the "Basic commands" section. "Aha, I knew it! I knew cd was a command for file navigation!"

"Yay! What's that mean?"

Dipper ignored her, thumbing through the commands. "Oh, I see…" Dipper hesitantly typed in ls to the terminal, and finally the laptop gave up some new information.

Ecimaw

Mabel looked at the lines. "Ecimaw? That sounds like a really cute dinosaur, with a really big mouth!" She put her hands up like a T-Rex and opened her mouth wide. "Rawr!" She pretended to eat Dipper's head.

"Mabel, get off me!" Dipper said, swatting her away, She laughed as he pulled out the journal and blacklight. "It's a code. Obviously, it's a code." He opened it to the section on codes, using the blacklight to see the quick guide. He scanned it quickly, "Huh, doesn't look like Caesar or Atbash though…"

"What's that at the bottom?" Mabel said, pointing in the journal.

"I haven't cracked that one yet, but it probably has to do with this word." He shined the blacklight on the word TRICKY written next to the code.

Mabel groaned. "Ugh, another password? And we have to figure out how this code works? Dang it, author, why you gotta make things so complicated?!"

Dipper sighed in frustration. "Ok, we can worry about that later. I don't think we need to decode it for the next step. This Ecimaw thing doesn't have a dot, so it's got to be a folder. So if we do this…" He double checked the book, then entered cd Ecimaw. Nothing visibly changed, however when he typed in ls again, this time the laptop showed something else.

Experiment_

Monitoring

"See, Mabel, that's what cd does. Now we're inside the Ecimaw folder." He started typing again. "And if we do it again for the monitoring fol-" Dipper cut off as, instead of going into the Monitoring folder, the laptop printed

Error: Monitoring is not a directory

"What's a directory?" Mabel asked.

Dipper frowned, reaching for the book. "I thought it was just a fancy word for a folder. And that monitoring thing should be a folder, it doesn't have a dot!"

"Well, maybe it isn't a folder?"

"Either that, or I don't know what a directory is." Dipper muttered. He flipped through the book quickly again, before sighing and opening back to the beginning. "I'm gonna have to do more than skim this to figure it out. While I do that, you find a book on codes and try to figure out what we're supposed to do with this password."

"What! Why do I have to figure out the code, that's your area of expertise!"

"You wanna fight with this book?" Dipper opened it to a page with several intimidating looking flowcharts.

"Ugh, no…" Mabel slammed her head down on the table. "I thought we were gonna get answers today, but now I have to do boring research? This journal thing sucks!"

"Yeah, it can be pretty frustrating," Dipper said, burying his face in the book again, "but it'll all be worth it when we figure out the mystery of the Author."

Mabel sighed. "Right, gotta clear Grunkle Stan's name," She stood up. "OK, Dip-Dop. I'll give it a shot."

Dipper looked up from his book to beam at her. "Thanks, Mabel."

Mabel let out a groan, her head falling down into the book in front of her. She'd done this several times over the last half hour, repeating a pattern of reading a paragraph or two before getting bored. Hey, it's not her fault that the stupid book was written by the least interesting person in the world! I mean, is it really necessary for a book about secret codes to spell out the whole history of secret codes?

Suddenly, a suave voice came from beside her. "Hey, Mabel. Looks like you're reading that book very closely."

Mabel sat up, the book sticking to her face. "Gabe!" She feigned looking around. "It is you, right Gabe? I can't exactly see right now."

Gabe chuckled, pulling the book off of her face. "The one and only." Mabel grinned at him, but before she could say anything, his bee puppet came back up. "Hey, how about a thanks for getting that book off your face," Gabe made it say, "I mean, it tasted awful!"

Again, before Mabel could reply, his book puppet jumped into the conversation. "What was that about books tasting bad? We kiss each other every show, and you've never complained!"

The bee puppet crossed its arms, turning away, "Yeah, it's called acting, sweet cheeks!"

Gabe jumped in in his normal voice, "Hey, whoah, you shouldn't talk to each other like that."

Mabel, witnessing the whole interaction, could only laugh awkwardly. Wow, he really never lets up the puppet act, huh. At least he was cute, the way he laughed along with her.

"So, what brings you to the library on this fine day, reading a book about," He glanced at the title, "secret codes?"

Mabel huffed "I promised my brother that if he helped me with my sock opera, I'd help him with his nerd stuff, solving codes and mysteries and junk."

Gabe seemed to suddenly lose interest. "Oh, I thought you might be researching for your next puppet show. I guess that's cool that you're helping your brother like that."

Mabel sighed, pulling the book back toward her. "I just wish it wasn't so dang hard, y'know? I don't know what I'm doing, this is his deal!"

Gabe frowned at the book. "Wait, are you reading the book from the very beginning?"

"Uh, yeah?"

Gabe laughed. "Well, you're right that you don't know what you're doing. When you're researching, you don't read the whole book," he explained in a patronizing tone.

Mabel laughed weakly in response. Yeesh, did you have to sound so mean about it? She didn't say that, though, instead she said, "So, uh, what am I supposed to do then?"

"Well, you look at stuff like the table of contents and the index to get the parts you need."

A small kid suddenly ran up to Gabe and tugged on his pant leg. "Mr. Gabe, the next show's supposed to start soon!"

Gabe smiled at the kid. "Alright, little guy. We'll be over there in a sec." He had his bee puppet wave the kid off. "Looks like duty calls. Text me later?"

Mabel forced a smile. "Yeah, sure, Gabe." He winked at her before walking off, which didn't make her heart flutter like it might have that morning. She sat back down at the table looking at the book morosely.

Gah, did Gabe really have to make me feel so stupid?!

Ok, so maybe he was a little rude about it, but he did give me good advice on researching.

Yeah, but he didn't have to be such a buttface about it!

Maybe it's just a thing where he was rude by accident, y'know. I mean, I've done stuff like that before, right?

Mabel shook her head, smacking her face. There she went again, overthinking things. The quicker this part of her life was over, the better...which meant she needed to get back to the nerd book. Hefting a sigh, she opened the book to the table of contents first. Nothing immediately stood out, no chapter called something like "Password based codes" or anything like that. Mabel wondered if maybe there was, but written fancier than she could understand.

She shouldn't have given it any thought, just gone to the index, but all these reminders of how bad she was at this research thing was getting to her for some reason. Mabel sniffled a little bit, considering dipping into Sweater Town for a while. Somehow though, in spite of not even glancing up from his book the whole time she'd been talking to Gabe, Dipper heard her and looked at her in concern. "Mabel? What's wrong?"

Mabel looked down into the book. Dipper waited for her to answer, brow furrowed in concern. Finally, Mabel said, "Dipper...do you think I'm stupid?"

Dipper blinked in shock. "What?! No, where is this coming from all of a sudden?!"

Mabel gestured vaguely at the book. "First, I was trying to read this stupid book from the stupid beginning, but I couldn't stay focused on it. Then Gabe showed up and made me feel dumb for not knowing to not read from the beginning, and I mean, this stuff doesn't usually bother me but it's important to figure this out for Grunkle Stan and I just…" She trailed off, sniffling again.

Dipper's expression darkened. "Wait, your boyfriend called you dumb?"

Mabel shook her head. "No, he just made me feel that way."

"That's not any better." Dipper muttered, scooting his chair to sit beside her. He pulled her into a sideways hug. "Look, Mabel," he said softly, "Just because you don't know how to do proper research doesn't mean you're stupid. It just means that you've never learned it before. There's lots of times where you've been smarter than me."

Mabel looked up at him forlornly. Dipper continued, "I couldn't figure out how to tell Wendy how I felt until I took your advice. You figured out who really founded Gravity Falls, when my best idea was burning our only lead. Heck, we wouldn't be in the library today if you hadn't pointed out how dumb I was being yesterday."

Mabel considered it for a moment, then wiped her sweater sleeve across her eyes. "I guess you're right." She smiled at her brother, returning his hug. "Thanks, Dipper."

"No problem," Dipper said. "Now, do you know what your next step is?"

Mabel nodded. "Yep, index is the next thing to check."

"Good idea, try looking at 'password', and just read the bit you need to know."

Mabel flipped to the index, seeing a few different page numbers to check. "Wow, that really does make this easier."

Dipper laughed. "Of course, nobody would like research if you had to read every book cover to cover." He looked back to his own book with a grimace. "Like what I'm having to do with this. I don't know what's wrong, so I don't know where to start looking."

Mabel gave him a thumbs up. "You'll figure it out, Dipper."

"So will you," he said, sliding back in front of the computer manual, "I know you can do this, Mabel."

He returned to his own book as Mabel took a deep breath. Right. I can do this. She grabbed a sheet of paper, and she marked down all the pages with the word password. There's not a lot of them. Maybe password codes aren't super common? She got her answer when she started checking the pages. All of them mentioned passwords as a secure way of storing information that has become more prominent in the age of computers. No codes that mentioned using passwords, though. She pouted, disappointed that her first search had been fruitless. But, like Dipper had said, she wasn't stupid, and she was going to figure this out.

She looked at the code again, hoping for some inspiration. For the first time, she noticed that there was a little drawing of a key next to the password. Maybe 'key' will get me somewhere? She returned to the index, quickly finding the word 'key'. As she was marking it down on her paper, though, she noticed that right under it was 'key phrase', and that just sounded like a fancier way of saying password. She made note of that too, and decided to check it first.

Looking at it, it looked like she'd finally hit on a code. The Vigenère Cipher? She read it carefully, looking at the accompanying chart as she did so. It didn't make much sense to her, but the book helpfully provided step by step instructions.

Step 1: Copy the message you wish to decode

Mabel grabbed the journal again, shining the blacklight on the message and copying it to her sheet of paper.

Step 2: Line the letters of the key phrase with the letters of the message (if the key phrase is shorter than the message, repeat it).

She did that step pretty easily, but step 3 was the confusing one.

Step 3: Go to the row with the letter in the message. Find the corresponding key letter in that row, the letter in that column is the answer letter.

Mabel read this step a few times before giving it a shot. Slowly, she did her best to follow the instructions, writing out the letters as she went. Her heart soared when, after tracing out the first 3 letters, they actually made a recognizable word. She wanted to tell Dipper right now that she'd got it, but she held back. Just imagine how much happier he'll be if I have the whole thing done! She went faster, confident now that this was right, and before long the message lay decoded in front of her.

"'The most impossible thing to decode is human social behavior,'" Mabel read aloud, "I beg to differ, Mr. Author!" A huge grin began to spread on her face, and Mabel let out the squeal that had been building for a while. "Dipper! I figured it out!"

"Shhh!" Dipper instinctively replied, then her words registered and he grinned with her. "Wait, really?!"

Mabel proudly slid the paper over. "See for yourself, Broseph."

He read it quickly, grin widening. "This is great, Mabel! What was the code?" Mabel slid the book to him in answer. "The Vigenère Cipher?" He read, then quickly looked through the instructions. "Huh, that's a neat code. More secure than something like Caesar or Atbash."

Mabel leaned her head back with a groan. "Ugh, don't remind me."

"Right, Ecimaw." In spite of herself, Mabel smiled at the image the word conjured in her mind. So cute! Dipper was still reading. "Somehow, it looks like guessing the key phrase here is going to be even worse than the laptop's password," he said, matching her groan, "At least then we knew the password was eight letters! This could be anything!"

Mabel cupped her chin, thinking. "Well, the journal had the keyword written right there, so maybe this one is on the computer somewhere?"

Dipper turned the laptop to face her, showing lines of gibberish. "I haven't seen anything like that yet. I found out how to open text files, but this whole experiment log is also written in code."

"Well, are there any other files?"

"There was that manufacturer file. Maybe knowing who made it will give us a clue?"

"Yeah! Open it, open it!" Mabel started chanting.

"Shhh!" Dipper hissed, turning the laptop back around. Slowly, consulting the book for every step, he navigated to the file and opened it up. It was very short, but immediately insightful.

Created by McGucket Labs

1979

"McGucket Labs?" Mabel said.

"Wait, Old Man McGucket?" Dipper asked, scratching his head. "What does he have to do with anything?"

"Maybe he's the author?"

"That doesn't make any sense. Where does Stanford fit into the picture? Although…"

Dipper trailed off, muttering to himself, while Mabel started rambling. "Maybe Stanford was his secret lover? Oh, that'd so romantic, using research as a cover for their forbidden love-"

"Ok, we're stopping there," Dipper cut in. "Maybe it isn't as crazy as I thought."

"Of course, my love story is genius!"

Dipper massaged the bridge of his nose. "Not the love story, McGucket being the Author! We need to go find him!"

Mabel leaped up with a fist pump. "Heck yeah! No more boring research!" She ran out as Dipper shushed her again. Time for some action!

Key: Dinosaurs

HKVASW NFLDTYM TEUKK UIQOOGMRMUCF, OFD CK'K QWG QDOMV.

Previous code: TUNNEL VISION RUNS IN THE FAMILY

Notes:

If you hadn't figured it out by now, my favorite part of the Gravity Falls community was the code breaking and theory crafting. I love that stuff. Also got some more old computer stuff in there. "ls" is like the most important terminal command out of all of them, yet for some reason the terminal computers we used in school didn't have it in the help menu. I guess it's so integral that they assume people know it going in? The Monitoring thing is also based on something that was borderline unthinkable to me as someone who grew up on Windows, so I'm once again inflicting that pain on Dipper.

Speaking of, we got another moment of sibling bonding, Gabe showing himself to be awful, and they're on the trail of McGucket a little earlier. I'm sure that won't matter. Probably.

On another note, I've been very happy to see the story do so well! Sincerely, thank you so much for reading and enjoying this story. I've loved getting all your comments on the first 3 chapters. Thank you all again, and have a wonderful New Year!