Fourth, I do NOT own Gravity Falls. If I did, the series never would've ended. And now, without further ado...
Chapter One: Everything is going to be OK.
Twelve-year-old Dipper Pines waved goodbye to his friends as the bus started chugging toward his home in Piedmont, California. His sister Mabel snuggled with her pig, Waddles, trying not to cry.
They were leaving Gravity Falls after their first-ever visit. Even though it had only been one summer, it felt like they had spent an eternity in the Falls to the twins.
"I'm going to miss them so much..." Mabel murmured.
"Me too..." Dipper replied as he opened the envelope from Wendy. To his delightful surprise, the letter it encased displayed an array of signatures from the many friends he had made on his adventures in Gravity Falls this summer.
"Mabel, look," He said, handing the letter to her. He enjoyed her expression as she traced the names of her friends.
"This- this is amazing," She said.
Neither knew what else to say and continued watching the Gravity Falls landscape. It was beautiful, much more so than Piedmont. The green grass danced with the wind amongst the hilltops, and through the luscious, thick forests peered a variety of animals... but not average animals. More like... creatures. Yes, creatures.
Awhile later, the Exiting Gravity Falls sign came into view.
All of the sudden, Dipper felt an odd sensation, like his chest was tingling. Just as he were about to ask his sister if she felt it too, he felt a harsh stab in his chest. The pain shot through him like a zap of lighting. It wasn't just a quick burst of horrifying pain, though, as it continued to linger and throb... He tried to scream, but found that he couldn't. He felt warm blood oozing all over him. He'd never felt this much pain in his entire life. He couldn't breathe. Panic overtook him. His heart beat very loudly. What was this? Was he going to die? Mabel still hadn't noticed, somehow. She was trying to stop Waddles from running around the seats, and was tugging the pig off a bench much further to the back.
Finally, it seemed Mabel had managed to calm Waddles down enough to pull him back to their seat. When she saw her bloody brother, she gasped and broke out in silent tears. Dropping Waddles, she screamed.
"DIPPER! Wh-What...!"
"Call... Stan..." He finally managed to gasp, before blacking out.
Mabel got the message, as twins tend to do, and she pleaded, "STOP THE BUS!" as she dialed Stan's number.
Stan answered the phone. "Mabel? Is everything OK? What's going on?" He said, hearing her now not-so-silent sobs.
"You gotta get over here! Something's wrong with Dipper! He's..." She hesitated.
"He's hurt really bad... like, about to die bad..."
You could almost hear the color drain from Grunkle Stan's face.
"OK, don't- don't go anywhere. It'll be OK, Pumpkin, we'll be right there, just- just tell me where you are,"
"We're right by the Exiting Gravity Falls sign," Mabel pleaded, "Hurry!"
"We will," Stan said, trying to hide his fear. "Don't hang up!"
Mabel continued to listen to the phone. She heard distant yelling and then a car door slamming.
"We're coming."
Ford's voice was now ejected through the phone.
"Can you describe what's... going on?" He asked frantically.
"It looks like he got stabbed o-or something... Something's tearing apart his body... It's not stopping!" Mabel now continued to sob.
"I'm scared, Grunkle Ford..."
"We all are, sweetie..."
Mabel spotted something distant on the road out of the corner of her eye. Their car! "I see you! Hurry... p-please..."
She watched as her Grunkles and Soos clambered out of the car and ran like the wind toward the bus. The bus driver was clearly confused as to what was happening as they climbed on and ran to the seat where Dipper lay unconscious, a now silent Mabel by his side.
The rescue trio stood aghast for a moment. It really was as Mabel had explained it. Like an invisible knife had stabbed him and was being dragged lower down his body, ever so slowly. His skin was ghostly white, and it was cold to the touch- so much so that he looked dead- but Dipper was still, somehow, breathing. It seemed like magic... if you could even call it that. The team snapped out of it and set to work. Ford ordered Stan to fetch the first aid kit from the car and try to stop Dipper's excessive bleeding. Soos comforted Mabel and cradled Dipper's head in his lap. Ford commenced to rapidly interrogate Mabel.
"Did Dipper say anything... anything at all?" He inquired.
"He only said 'Call Stan', then h-he... you know..." Mabel was on the verge of tears again. She hated seeing her brother like this.
"Did he say anything else?"
"No... It kinda looked like he w-wanted to but h-he couldn't..."
"Hmm... odd..."
"Y-yeah..." Mabel was now looking at her feet. "When did- this-" He glanced toward the wound, "Start?"
"J-Just as we were c-crossing the town border,"
He thought for a moment. His face changed to that of realization, horror, confusion, and panic all in one.
"We need to get him back into the town...! Excuse me, sir!" He spoke to the bus driver now. "Turn the bus around and head back to Gravity Falls! Stanley, Soos, get the car out of the way. Make room for the bus."
The two nodded and rushed off the Speedy Beaver. Ford then took Soos's place holding Dipper upright.
"Everything is going to be OK," He said, more or less to himself, as the bus slowly turned around.
Stanford Pines looked into the eyes of his frightened great-nieces face, which was stained with tears and fear. He was equally as terrified, but for the sake of the child he hid it. The only thing he could manage was:
"Everything is going to be OK."
They both wanted to believe it. Believe me, they tried. But they weren't so sure.