Mabel Pines crept down wooden stairs illuminated by a single lightbulb hanging from the ceiling. She was overwhelmed with confusion and fear; she half expected some horror movie monster to jump out of nowhere and eat her. She clung to her twin brother's arm as the two descended.

"You said Ford came down here?" Mabel asked. Her brother Dipper nodded. He had woken her up in the middle of the night claiming he had seen their great uncle, Stanford Pines, come through this secret passageway. Sneaking down to the gift shop of Ford's business, the Mystery Museum, they had discovered the vending machine was a door hiding a mysterious staircase leading underground.

The staircase Mabel was now descending.

"Yeah," Dipper said. "He was moving weird, too. Like he was sleepwalking. Or zombified." He said this last part in an ominous voice.

Mabel nudged him in the side. "Quit it. This is too creepy for zombie jokes."

They reached the bottom of the stairs. Mabel's bare foot scuffed against the rough wood, driving a sliver into her heel. She hissed, bending down to pull it out. She should've at least thought to put on socks, like Dipper.

"Mabes, look," Dipper said.

They were in a small, bare room at the base of the stairs. Old wooden supports jutted out from bare rock on two sides, with rusty metal pipes lacing the top of the walls. In front of them, opposite the stairs, a brick wall displayed cobwebs, grime, and an elevator set into its mortar.

"Do — do you think Grunkle Ford went down there?" Mabel asked. Her voice echoed dully around the small room.

"Looks like it," Dipper replied, taking a step toward the elevator.

"W-wait!" Mabel grabbed his arm. "That thing looks really old. What if we can't even get inside?"

"We might as well try."

"What if it breaks down while we're in it and we're trapped in there forever like The Twilight Region? We can't go in there!"

"Mabes—"

"But then what if Ford is hurt down there? O-or what if he's doing something secret and would get angry at us for following him? I just barely got on his good side again, Dip, I can't make him mad again! B-but he could be hurt o-or need our help o-or—"

"Mabes!"

She stopped and looked at him.

"Mabel," Dipper said slowly, "we're going into that elevator."

"Of course we are," Mabel said, "but—"

"Then why are you freaking out about it?" Dipper demanded.

"Because I have to freak out about it!" She stomped across the room over to the elevator and reached for the doors. Then she shied back, staring up at the imposing metal doors.

She heard Dipper's muffled footsteps behind her after a few moments. "You done?"

Mabel took a deep breath, nodded, and braced her hands on the elevator doors.

It took the twins a minute or two to force the doors open. With one on each side, pulling apart from the tiny space in the middle, they managed to slide the doors open enough to slip through. As she turned to go sideways through the opening, Mabel noticed a keypad to the side of the elevator, and felt a sudden relief at not having to guess a code to open it.

Once both twins were in the elevator, it rumbled, and the doors closed again. Mabel instinctively linked her arm through Dipper's, watching anxiously as metal confines enclosed them in total darkness. She wasn't claustrophobic or anything; in fact, she liked small spaces. She didn't like old abandoned elevators that may or may not plunge her to her doom.

The elevator started moving with no plunging involved.

"What do you think is down there?" Mabel whispered, her voice small in the darkness.

"Grunkle Ford," Dipper replied.

Mabel elbowed him. "You know that's not what I meant!"

The elevator thudded to a stop, and the doors slid open. A distant yellow light reached Mabel's eyes, but she couldn't see what lay between it and her. It shown through what looked like a doorway, but it was far enough away that Mabel feared running into something or tripping on her way over to it.

"C'mon," Dipper whispered. "I think that's Ford's light."

"What if it isn't?" Mabel whispered back.

"Then we'll find out."

Dipper stepped out of the elevator, pulling Mabel along with the arm that was linked with hers. They started cautiously down the passageway, stepping slowly, going straight towards the light, which was ahead and slightly to their right.

As Mabel's eyes adjusted, she started to make out shapes in the darkness. The twins were walking through a narrow passageway through rows of bulky objects that formed walls around them. At the end of the passage was the doorway through which the light was showing, but also what appeared to be a window to the left, with a few rays of light peeking around its corner.

The twins made it to the doorway without running into anything, and stopped just before it, glancing at each other. Dipper nodded, and Mabel bit her lip.

They stepped through the doorway.

The light they had followed came from a lantern on the floor. Next to it, sure enough, was Stanford Pines, kneeling on the ground and staring up at the far wall. He didn't see the twins.

Mabel suppressed a gasp as she looked around the room. They were in a cavern of stone, its walls held back by wooden supports that crisscrossed the walls. At the far end of the room, where Ford was staring, was a giant metal triangle, upside down and easily five times as tall as Mabel. A perfect circular hole in its center reminded Mabel somewhat of an upside-down Bill Cipher.

And Ford was simply sitting and staring at it.

Mabel and Dipper exchanged looks again, and Dipper opened his mouth, but Mabel shook her head violently. She had no idea what to do, but she had a really bad feeling about disturbing Ford. And about this room. And about the fact that there was a secret underground vault beneath the Mystery Museum.

Dipper gestured silently towards Ford, and Mabel shook her head again. Dipper spread his arms in a "why not?" gesture, and Mabel stabbed the air with a hand to show her frustration. The two kept gesturing violently at each other, Dipper clearly wanting to get Ford's attention and Mabel wanting to get out of there before he—

"Kids?"

The twins froze.

Ford had turned to see them and was staring at them with wide eyes. Mabel felt her blood freeze up in her arteries as she braced herself for him to start yelling at them.

"How did you get down here?" Ford asked softly.

Mabel didn't answer, too shocked from not being yelled at.

"We followed you," Dipper said, taking a small step towards his great uncle. "Grunkle Ford. . . What is this place?"

Ford blinked slowly at his grandnephew, then turned back to look at the humongous triangle across the room.

"I don't know."

Mabel's eyes widened. "What do you mean you don't know?"

"I mean. . . I know. . . I built it, but. . . I don't know."

Mabel and Dipper glanced at each other, then went to Ford's side. Dipper kneeled next to him, Mabel standing nearby.

"Something happened down here," Ford continued. His voice sounded distant, like he wasn't really talking to the twins, but to himself. "Something terrible. It's coursing through me. . . Can you feel it?"

He looked up at Mabel.

"Um — I—" She could feel something, but it was mostly a sense of foreboding from being down in this ominous cavern. "Not really."

Ford nodded like he expected that, then gazed up at the triangle again. "Why can't I remember? I know something happened down here, I know it, but. . . I don't know what. I can't even. . . remember what this is."

"The triangle thingy?" Dipper asked.

"Yes. . . Until Mabel gave me my Journal, I. . . I had forgotten this laboratory was even down here." He looked up at them again. "How could I forget that?"

Mabel glanced past him to see the Journal on the floor in front of him. Its maroon cover gleamed in the lantern light, and the bold black 3 sat comfortably atop the golden six-fingered hand. Mabel had found the Journal out in the woods weeks ago, but had only given it back to its rightful owner, Ford, earlier that same day. It had been stolen from him years ago.

"Wait," Dipper said, "you forgot there was a big cave underneath your own house? With this huge upside-triangle thing that you built?"

"Yes," Ford said softly. "There's something else. . . something important that I'm missing. . . something. . . to do with the Journals. . . ."

Dipper opened his mouth to reply, but Mabel shushed him with a shake of her head. Ford was onto something here, she could feel it. His train of thought couldn't be interrupted.

"The Journals. . . I wrote three Journals. . . all three. . . You need all three to. . . activate the. . . ."

He gasped and jerked back.

"Lee!"

The singled shouted word reverberated around the cavern, bouncing off the metal triangle and back into Mabel's ears. A leeching silence followed it, sucking all feeling off Mabel's skin. A shiver ran up her spine.

"G-Grunkle Ford?" Dipper whispered.

Mabel looked down and nearly jumped back in surprise. There were tears on Ford's face. They flowed freely down to his chin, dripping onto his lap.

Stanford Pines was crying.

"F-Ford!" Mabel dropped to her knees beside him, wanting to comfort him somehow, but having no idea what to do. "Wh-what is it? Who's Lee?"

Ford buried his face in his hands. His shoulders shuddered with a deep, broken breath.

"Lee. . . ," he whispered. "How could I. . . how could I forget. . . ?"

"Forget?" Dipper asked. "Grunkle Ford. . . Who is it? What happened?"

Ford wouldn't answer. His breaths were spasmodic, his eyes covered by his hands. Mabel found her gaze tracing the outline of his fingers. Six fingers on each hand. The mark of the Author of the Journals.

Finally, Ford's breathing settled into a normal rhythm, and he sat up, wiping his eyes. With one last deep breath, he turned to the twins.

"Go back to bed."

Mabel started. "What?"

Ford's eyes were hardening back into their standard steel. "I said, go back to bed. You two aren't to be down here."

Mabel and Dipper shared a shocked look.

"Grunkle Ford. . . ," Dipper began. "Are you okay? You were just—"

"I'm fine," Ford said, his voice clipped. "Now, go back to the elevator, and — oh, never mind. I'm coming with you."

He got to his feet, bracing a hand against his knee, tucking the Journal into his coat and picking up the lantern. Mabel and Dipper jumped up too, their twin senses going haywire. Something was wrong with their grunkle, who was very obviously hiding something from them, and they didn't know what to do about it.

So they let themselves be led away.

The elevator was more cramped with all three of them, and Ford's lantern cast eerie shadows around the small space. Mabel and Dipper spent the elevator ride mentally daring each other to speak up first. Neither was brave enough.

When the elevator shuddered to a stop, the Pines stepped out and started up the staircase back to the world above. Mabel's eyes traced the collar of Ford's trenchcoat as she followed behind him, trying to see if he looked tenser than usual. She found herself getting frustrated — of course Ford would pretend like nothing had happened after they had seen him cry. She never thought she would see him break down like that, and now he wouldn't even own up to it.

Mabel's bare foot found the top of the stairs, and she moved into the gift shop. Ford waited by the vending machine until Dipper had joined Mabel, and then closed it behind them. It swung shut like a door, sealing with a slight sucking sound.

"Good night," Ford said to the twins.

Nope. Mabel couldn't just leave him with him acting like this. They had just made up earlier in the evening, and she didn't want him mad again, but he wasn't trusting them. Again. Not even enough to tell them why he was so sad.

"Grunkle Ford," she said carefully, brushing her hand against Dipper's to take some of his courage. "We'll go to bed, but you have to tell us what just happened in the morning. We want you to trust us."

She could see Dipper nodding in her periphery.

"Please?" she added for good measure.

Ford studied the two of them. "We can discuss it later," he finally said. "For now, get some sleep, alright?"

Mabel found this answer vague and unconvincing, but it was better than nothing. "Okay."

Dipper stepped forward and hugged Grunkle Ford. "Good night." He pulled back and smiled up at his great uncle.

Mabel wanted to follow suit, but wasn't sure how Ford would react. She ended up giving him an awkward side hug before moving back towards Dipper, who was in the gift shop doorway. "'Night."

Ford offered a faint smile. "Good night."

The trek up to the attic was silent until the twins were back in bed. Dipper took a deep breath. "Okay, what did we just see?"

"I don't know," Mabel said, staring up at the rafters in the darkness.

"What do you think that big metal thing was? And who Lee is? And why—"

"Dipper," Mabel said wearily, "can we get some sleep?"

There was a beat of silence. "Okay," Dipper replied. Mabel could tell he was reluctant to stop talking — he figured things out best by thinking out loud — but she couldn't stand to listen. A heavy weight had descended over her chest, making it hard to think. Ford still didn't trust her. He was confused about something, something that made him — him! — cry, and he didn't trust her or Dipper enough to tell them.

She thought they had made some progress earlier that night, but. . . apparently not.

So instead of thinking about it, she'd rather just have gone back to sleep.

"Mabel," came Dipper's voice in the darkness. He paused before continuing. "I'm sure Ford will tell us about it in the morning. He seemed disoriented, that's all."

"Yeah," Mabel said noncommittally. She wasn't so sure.

"Good night, Mabel," Dipper said softly.

Mabel rolled over and closed her eyes. She didn't respond.