"Stanford!"

Stanley threw his arms out and hugged his brother tightly. Ford stood there stiffly. When Stanley drew back, Mabel could see the shock in Ford's eyes.

"Lee. . . How?"

Lee put a hand on Ford's shoulder. "Brother. I've been waiting for you for thirty years."

"But you were. . ."

"Don't you remember? There was an accident. I got trapped down here. I've been here ever since, living off canned beans and fighting off the last of your monsters. I thought you would come back, but. . . you never did."

"That isn't what I remember at all," Ford said. "But my memory hasn't exactly been reliable lately."

Mabel thought back to that night in the secret basement. The expression of Ford's face as he stared up at the portal was burned into her memory. The tears he had shed for his brother had glistened as they had fallen to the ground. He couldn't have remembered wrong. Could he?

"Follow me," Stanley said. "Come see where I've been all these years."

He bent down and picked up Ford's flashlight, handing it back to his brother with a smile.

Ford took it, but didn't smile back.

Stanley started down the tunnel.

"Wait," Mabel said. "Isn't the monster back there?"

Stanley turned. "Oh. Yes. I stashed the body in another tunnel. There are all sorts of monster corpses littered around here. But I keep the path to my hideout clear."

Mabel and Ford followed him through the passage. They didn't say anything, but both of them stayed back a little.

"Mabel," Ford whispered. "Something is wrong."

"That's not your brother, is it?"

He shot her an impressed look. "I don't think it is. What tipped you off?"

"You. You looked suspicious. And you can't be wrong about him being in the portal. Not after the other night."

Ford nodded. "That's what I was thinking too. There are plenty of creatures who can look like something they're not. And something else he said. . . 'all sorts of monster corpses.' There was only one cage back there, and the harder I think about it, the more I only remember one creature. At least. . . the last time I was here."

"What kind of creature?"

"I'm not sure."

Mabel and Ford abruptly cut off their conversation as Stanley came to a stop in front of them. Lee — or, the Lee imposter — stepped up onto a rocky ledge and pushed back a tattered cloth hanging down from the ceiling. "Here we are."

The room beyond looked like the rest of the tunnels, except littered with empty cans and metal scraps.

"It's not much," Lee said with a chuckle. "But it's home."

"How come you couldn't just leave?" Mabel asked, glancing at Ford. He nodded, almost imperceptibly. They'd ask the imposter some questions to see if they could get him to reveal himself.

"I couldn't get past the security room!" Lee replied. "We came down here all the time, but Fordsie here always put in the code. I didn't dare try. I know how dangerous that thing is. It's ridiculous, but Fidds just couldn't help himself."

Ford gasped.

Mabel jumped at the force of it. Ford stumbled back, hitting a nearby rock wall. His eyes were wide, his breathing heavy.

"Gr-Grunkle Ford?"

He shook his head. "I-I'm fine." Even though he obviously wasn't. He met Mabel's eyes, then glanced to the Lee imposter. Mabel caught the message: Keep him talking.

Mabel forced herself to turn away. Ford's labored breaths still filled the space behind her.

"So, um, Lee, what kind of monsters are down here, anyway?"

Lee blinked before his eyes focused on her. "Oh. I don't really know their fancy science names. Again, that was Ford's job."

"What about that one you just fought? What did it look like?"

Lee squirmed a little. His hand went up to his grey hair. "It was, well, this big brown thing. I wouldn't want to scare you with too many of the details, not a cute little kid like you. Who are you, anyway?"

Should she tell the truth? "I'm, um, I'm Stanford's great niece. Yours too, I guess."

"You do look like a Pines."

"Thanks? Um, will you show me around your — cave?"

She was bad at this game. Luckily, the Lee imposter was too.

"Sure." He spread his hands out. "My cave."

Dang it. She was hoping she could get him to turn his back. Maybe he was better at this game than she thought.

"I'm sorry," Ford said, leaving the wall he'd been leaning on. "I had, ah, a brief asthma attack."

"It's no problem," Stanley replied.

Mabel and Ford glanced at each other. Now they definitely knew Lee was an imposter: Ford didn't have asthma.

"Say, Ford," Stanley said. "Do you still have those Journals of yours?"

"No. We're actually down here looking for them. Do you know where any of them are?"

"Can't say that I do."

They fell into awkward silence.

Ford opened his mouth. "Well—"

Something clattered in the distance.

"What was that?" Mabel asked. "Is something out there?"

"Oh," Lee said, "the rocks shift all the time." His face looked nervous.

"It might be another monster," Ford said. Mabel was surprised to see fear on his face. "Lee, I haven't been in the game for a long time. Maybe you should go out and check?"

"I don't think there's anything out there."

"Just in case?" Ford pleaded.

Something flickered across Lee's expression. "All right, fine. I'll be right back."

He stepped out of the cave.

As soon as the curtain fluttered down after him, Ford turned to Mabel and dropped to a knee to get at her level. The fear in his eyes was completely gone, and only then did Mabel realize he'd been faking it.

"Mabel, I remember. I remember everything."

"Everything?" Mabel whispered.

"Everything about the bunker," he conceded. "But I know who that man is. And it definitely isn't my brother. It isn't even a man."

"Who? What is it?"

"He was one of the experiments we brought down here. We found him as an egg. Lee affectionately named him Shifty."

Mabel's stomach dropped. "You mean. . ."

Ford nodded. "We're dealing with a shapeshifter. One who can turn into monsters even I could never defeat."

~~~~~

Candy draped herself over an old-timey recording machine, fiddling absently with the tapes. "It's so boring in here," she moaned.

"Yeah," Dipper said, "but Grunkle Ford said to stay in here."

"So do you just do everything he says?"

Dipper frowned. "Candy, he wouldn't let any of us come along unless we followed his instructions. Don't you remember?"

Candy made a "pfft" sound and let her arm swing down. It hit a stack of papers, flinging them across the room.

"Aw, c'mon, Candy. Now we gotta clean these up." Dipper bent down with a sigh.

He had already gathered about half of them before Candy joined him.

"Candy. . . ," Dipper said. "Have you read any of these papers?"

"It's just a bunch of math stuff," she replied.

"What if they have clues about the Journal?"

"If you wanna read them, go ahead." She grabbed the last of them off the floor and handed her pile to Dipper.

Dipper frowned again, this time at Candy's back. He'd suspected for a while that she might have a crush on him, but then she did rude little things like this. Was that just her awkward way of crushing, or was he misreading her?

He shook the thoughts away and started flipping through the papers in his hand.

Candy was right; it was a bunch of math stuff. But Dipper kept looking, a little ways through the stack, he pulled out a page of written notes.

"Here's something. Huh," he said. "I don't think this is Ford's handwriting."

He traced the words with a finger. "Experiment #210. The Shapeshifter. This unnerving creature can turn into anything it sees. Stanford finds 'Shifty' delightful, but I can't help thinking. . . what if it tries to pose as us one day? What if got into town and could impersonate everyone? Once again, Stanford is blinded to the dangers by his scientific interest."

There were a bunch of technical terms after that, talking about the Shapeshifter's qualities and abilities. Dipper's eyes skipped down to big, blocky words scrawled at the bottom of the page.

"SHIFTY ATTACKED ME! HE TIED ME UP AND TRIED TO POSE AS ME IN FRONT OF FORD! HE'S TOO DANGEROUS!"

Then, at the very bottom, in more neat, deliberate capitals. "PLACED IN CRYOGENIC STASIS."

"Who wrote that?" Candy asked, once Dipper had finished reading aloud.

"Ford's assistant, looks like."

"Those noises we heard. . ."

Dipper looked up at her. "Do you think that. . . was. . . ?"

They stared at each other with wide eyes. It took a moment before Dipper's voice would work again.

"We gotta go find Mabel and Ford!"

~~~~~

The next thing Mabel knew, Ford was pulling a gun out of his pack. "Get out your grappling hook," he instructed her.

She did as he said. The weight of the grappling hook in her hand was surprisingly comforting. "Won't he know that we're onto him?"

"I can't think of any other ways to stall." He cursed under his breath. "Scrabdoodle! We've let him corner us. We have to get out of here."

"Scrab. . . doodle?" Mabel asked.

"It's something Fiddleford used to say."

"Who?"

"My—"

"See, I told you, no monsters out here!" Stanley — no, Shifty — had returned. He paused in the doorway, his hand still pushing up the curtain. "What's with you two?"

Ford laughed. "Oh, we're just jumpy, is all. You know me. Your paranoid brother."

Shifty-Stanley's eyes narrowed.

"Well, this has been really nice," Ford continued, "but don't you think we should get back to the observation room and get out of here? We'll go back home. Together."

Shifty-Stanley grinned. "Of course! I've been waiting for you to give the word."

"Great." Ford stepped towards the entrance. Mabel followed, staying deliberately behind her great uncle.

"Wait a second," Shifty-Stanley said. He didn't move from the entrance. "I believe you have something I need."

"What do you mean?" Mabel noticed Ford's hand tighten ever so slightly on the gun.

Unfortunately, Shifty-Stanley noticed too.

"Give me the Journal, Stanford," he said. "I know you have it."

"I told you. We don't have any of them."

"Cut the games, Ford, we all know you're lying!"

"Stop wearing the face of my brother, then maybe we'll talk!"

Shifty-Stanley paused. Then his face stretched out into a grin that split the skin around his lips. "All right," he said. His voice deepened. "We'll both stop playing, then."

Stanley's skin melted off Shifty's face.