"I think I see it!"

Mabel nearly bumped into her brother as he stopped in his tracks, pointing at something ahead. "Is that a light?" he asked.

Ford switched off his flashlight, throwing their little group into darkness. Once Mabel's eyes adjusted, she could see what Dipper was talking about. A faint light at the end of the tunnel winked at them.

Dipper and Candy cheered and started running for it. Mabel stayed next to Ford, who switched his flashlight back on and went at a slower pace.

"So what's your plan, Grunkle Ford?" she asked.

"There are pipes littered throughout the shallower tunnels. They're still working, as your brother discovered earlier. I want to find one and wait for the shapeshifter. Once he finds us, we'll release the water from the pipes and let them hit him full on. Hopefully, he'll shapeshift into something that can swim, something vulnerable. I'll shoot the water with my stun gun, and it should knock him unconscious, or at least disable him for long enough to get him back into cryogenic stasis."

Mabel frowned. "Cryogenic stasis?"

Ford nodded. "Those tubes back in the lab were created to cryogenically freeze subjects. After Shifty got out of hand and attacked Fiddleford, we froze him. Then we woke him up later, when Lee came, but he was still too dangerous. We had to refreeze him. And that's the last time I remember seeing Shifty. I don't know how long he's been awake, but not long enough to tunnel aboveground, fortunately."

"Fiddleford," Mabel said. "You mentioned him earlier. Who is he?"

"He's F," Ford said. "The assistant in my Journals."

Mabel's eyes widened. "You remember him?" she asked excitedly.

"Shifty tipped me off when he called him 'Fidds.' His name was Fiddleford McGucket."

"Fiddleford McGucket," Mabel repeated, trying it out. "That's a weird name."

"He was a strange person. But a brilliant one. He and I were good friends. We worked together for a while before Stanley came and joined us." Ford's eyes narrowed. "He didn't seem like the type to steal my Journals. But something happened between us, something important. He's not out of suspicion."

"Where do you think he is now?"

"I have no idea."

They had reached the end of the tunnel, and their next few steps carried them into the lab. The florescent lights overhead cast harsh shadows onto the rock. Mabel shut her eyes for a moment to give them time to adjust.

Dipper and Candy waited in the door between the bunker and the lab. "There you guys are," Dipper said. "So now what?"

"Follow me," Ford instructed.

He led them a few yards into another tunnel, over to a thick, rusty pipe that disappeared into the rock above. "We need to lure him here," Ford said, putting a hand on a large wheel that jutted out of the side. "Then we can blast him with the water in this pipe and put an end to this."

"He wants the third Journal," Mabel said. "We could bait him with that."

Ford frowned. "I don't—"

"I'll do it," Candy said. "I'm fast."

"Me too," Dipper volunteered.

Ford hesitated a moment before pulling the Journal out of his pack and handing it to Dipper. "If Shifty gets this, or it gets damaged, you both are in huge trouble."

"Message received." Dipper gave Ford a casual salute.

"Go back out there and get his attention, then run back here. Make sure to get behind the pipe with Mabel and me."

Dipper and Candy nodded before dashing away again.

Ford turned to Mabel. "Stay behind the pipe and keep your grappling hook ready. I'll turn the wheel once Shifty is in position." He extracted his stun gun from his pack. "Hold this for now."

Mabel held it at arm's length before gently setting it on the ground. Knowing her luck, she'd probably shoot Ford with it and doom them all.

Ford pushed at the wheel to loosen it up, but it made such a horrible screeching noise that he only did it once. Mabel sat on the ground, shifting on the rock.

And they waited.

"Grunkle Ford," Mabel said after a while, "once we stun Shifty, what are we going to do with him?"

Ford glanced at her, resting his hand on the wheel. "I don't know," he admitted. "At first I thought we should just refreeze him, but the cryogenic tubes might not even work. He somehow got unfrozen in the first place, after all."

Mabel studied his face in the faint light that spilled into the tunnel from the lab. "You mean. . . you want to kill him?"

Ford sighed and looked away. "I don't want to. Shifty was like. . . like a pet, in the old days. Lee just adored him. But he's too dangerous to leave unattended, and I don't think I can contain him."

"Unless the cryogenic tubes work."

"We'll try," Ford promised. "And if it comes to it. . . Well, if you want to be a monster hunter, Mabel, sometimes you have to kill creatures that are trying to hurt you."

Her eyes dropped to the ground. "I know."

They lapsed into uncomfortable silence. Mabel traced the patterns in the rock with one hand and grasped her grappling hook in the other. Would she have the courage to attack Shifty with it if she had to?

A roar shook the air.

Mabel jumped to her feet, heart hammering in her chest. "He found them!"

"Stay behind me," Ford said.

A few agonizing moments later, they heard tennis shoes slapping on the rocky floor. "Dipper, come on!" Candy shouted in the distance.

They raced into view. Dipper had the clutched the Journal to his chest. "He's right behind us!"

Candy reached them first, swinging around the pipe and coming to a stop by Mabel.

"Dipper, hurry!" Ford shouted as Shifty came into view. The shapeshifter looked like a giant frog now, with lumps of flesh that squelched as he moved.

Dipper tripped.

"Dipper!" Mabel screamed. She started to run for him, but Ford pushed her back with an arm before grabbing his gun and running after Dipper himself. Mabel crashed into Candy, losing sight of her brother. She got to her feet just in time to see Shifty grab the Journal with a long, sticky tongue.

"Give that back!" Ford bellowed, shooting at Shifty. The shot crackled on Shifty's skin and dissipated, leaving no effect. Shifty laughed, the sound dancing around the Journal, still held by his tongue. Ford shot again, but to no avail.

The grappling hook suddenly felt heavier in Mabel's hand, as if it were trying to get her attention. She looked from it to Ford to Shifty, her thoughts exploding into panic. She had to help — she couldn't just stand here — move, Mabel!

She ran forward and shot her grappling hook at Shifty.

The hook speared straight through Shifty's tongue and hit the rock wall. The Journal — as well as a good portion of the tongue — fell the ground as the hook recoiled back to the gun in Mabel's hand.

Shifty bellowed, Ford ran forward to get the Journal, and Mabel just stood there, repulsed. She couldn't take her eyes away from the severed tongue, discarded on the ground, leaking blood out onto the stone. . .

"Mabel, move!" Dipper shouted.

She snapped out of her trance to see Shifty, in his true form, staring at her with rage in his pink eyes.

Scrabdoodle, said her brain.

Shifty charged.

Mabel dove out of the way, once again falling on top of Candy. Ford shot at Shifty again, who bucked at the electricity this time, stopping and roaring in pain. The stun gun could affect him in this shape, then — but it wasn't enough, because Shifty only paused for a moment before turning and going for Ford.

Ford shot again, but Shifty dodged and tackled Ford from the side, wrenching the Journal out of his grasp.

"No!" Mabel wasn't sure who shouted it — maybe it was all of them — but she, Candy, and Dipper all ran for Shifty and Ford. Mabel almost shot the grappling hook again, but she didn't dare risk hitting Ford — hitting the tongue earlier had definitely been a lucky shot.

She'd almost reached them — she could see the Journal, clutched in Ford's six-fingered hand — when something slammed into her from the side.

Everything disappeared in a sudden rush of murky green. It took Mabel a few aching seconds to realize she was wet — wet with water from the pipe, which was carrying her down the tunnel. Her entire body throbbed from the force of it, including her lungs. No, wait — her lungs were throbbing because she couldn't breathe.

She thrashed around in the water, but there was no escaping the rushing current that held her captive. Spots danced around oxygen-deprived eyes that strained against the dirty water. Her world turned sideways and upside-down and inside-out until she didn't even know if she was still moving anymore.

Then she hit something solid, and everything went black.