Dipper looked up from the journal when he heard running water. He had come to a small river in a sunny patch of the forest. Mabel came up behind him with something in her hand.

"Look, Dipper! I found the cutest caterpillar!" She held out one finger to show Dipper the fuzzy creature resting on it. She giggled. "It tickles when he walks."

Dipper glanced over without much interest. "Cool, Mabel." He looked down at the book again. "It says here that this river is called the Commutatus Fluvius, and that it has never been studied. Something about the other creatures in the forest warning Ford about it. Hmm, I would have thought that he'd test it out anyway." He flipped through a couple pages, looking for more information.

"Come on, Dip, that stuff is boring." Mabel said, petting the caterpillar. "Let's go back to the Shack."

"But Mabel, if I can figure out what the deal is with this river, then maybe Ford will finally let me work with him!" Dipper pulled out a test tube from his vest. "I have to show him that I can research this stuff too." He stepped onto the bank of the river, leaning over it with the tube in one hand and a lid in the other. "Just a couple drops…"

Behind him, Mabel was trying to tickle the caterpillar. She accidentally nudged it off her finger and it fell into the sparse grass. She exclaimed and went down on her knees, trying to find it. She saw it off to the side and turned quickly, bumping Dipper as he went to scoop up some water from the river.

"Ah!" Dipper yelled, tumbling into the cold water. He gasped as his head came above the surface and kicked his legs to stay afloat. "Mabel!"

"Oh, sorry, Dipper!" She ran to the bank of the river and tried to grab him, but he had gotten swept away from the bank.

Dipper grumbled to himself as he paddled towards the shore. The river was not fast moving or dangerous, but it was extremely cold. He grabbed Mabel's outstretched hand as he neared her and she hauled him onto dry ground.

"Oh man, that's cold!" Dipper said, standing up and shivering. His clothes were completely soaked and his hair was hanging down in his face, streaming with water.

"Sorry!" Mabel said again. She wiped her wet hand off on her sweater and grabbed Dipper's journal. "Let's head back and get you some dry clothes."

Dipper nodded and followed her back to the Shack. He was shivering worse than ever, and starting to get itchy. They entered the house and went upstairs to the attic, where Dipper put on some fresh clothes and Mabel put the caterpillar on her dresser.

"Why are you two back so early?" Stan asked, entering the room.

"Dipper fell in the river," Mabel said, trying not to laugh and pointing to the pile of sopping clothes at the foot of Dipper's bed.

Dipper shot her a look, scratching his leg distractedly.

"Aw, tough luck, kid." Stan said. "Well, since you guys are here, want anything for lunch?"

"Peanut butter sandwich please!" Mabel said.

"I'll have a salad or something." Dipper said, still a bit grumpy.

"A salad?" Stan asked, "Don't know if we have any. I'll bring you a sandwich, too." He marched out of the room and down the stairs.

"Gee, thanks." Dipper muttered. He rubbed his ear, which was also bothering him.

"At least he's making us lunch," Mabel said, "That's nicer than normal." She could see that Dipper was still upset, but she didn't understand why. "What's up, bro?"

"Nothing, I just itch all over." Dipper said, continuing to scratch. "I must have gotten a million mosquito bites." Mabel continued to look concerned. Dipper sighed. "Nothing against you, Mabel. Sorry for being grumpy. Could you scratch my back?"

She laughed a bit. "Wow, that must really be bothering you." She walked over and scratched his back a bit through his shirt. She noticed something odd as she rubbed her hand up and down.

"Hey Dip, I think you've got something in your shirt." She said curiously.

He looked over his shoulder. "Yeah, I feel it too. Just a sec." He walked into the bathroom by their room, still rubbing both his ears. They felt weirdly soft and floppy. Like the cartilage had dissolved or something. He closed the door to the bathroom behind him and pulled off his shirt. He couldn't see any evidence of bug bites, though he was still itching like crazy. He checked inside his shirt, but he didn't see anything that could have caused the weird padding he felt beneath Mabel's fingers.

He scratched his lower back. "What the-?" He said out loud. There was definitely something soft on his back. Maybe some moss or weed had gotten stuck to him when he fell in the river? He tried to pull it off, but it seemed attached to his skin.

Suddenly, he felt a jolt of pain course through him. He cried out, falling to the bathroom floor.

"Dipper?" Mabel's voice came from outside the locked door. "What's up, bro?"

Dipper writhed on the floor, pain wracking his entire body. He groaned, but couldn't say anything. With the strongest jolt of pain yet came a darkness at the corners of his vision, and he blacked out.