They held hands. Dipper waited, and then something was different, but it was hard to tell what. "Pine... I wouldn't ask this of you, if there was any other way. But... I need a vessel. A body, to travel in, like those cars you tell me about."
"I don't understand why it can't be Mabel." Dipper frowned.
Bill sighed. "I don't know, either. But I know, for some reason, it has to be you. Here... Take my hand, and that'll seal the deal..."
Dipper trusted Bill with his life. With all his secrets. Maybe because Mabel was the only one he would ever tell, and she already knew most of those things anyway. But he was uncertain, for a moment. Something warned him, something told him not to do this.
He took Bill's hand. "I'm sorry," said the triangle, before Dipper felt himself yanked away, by Bill's hand, into the air, now weightless, floating. Bill flew into the copy of Dipper he saw, the one standing where he stood, and suddenly things returned to normal.
"Did it... Did it work?" Mabel asked.
Dipper's form, slumped on the floor, slowly stood and opened his miscolored eyes. He grinned. "It did, Star, it really did."
"Woah... What happened?" She was in shock, staring at him, a little afraid.
"Oh... I'm borrowing your brother's body. It's... It's only to escape from this cave with." He smiled.
"Oh, okay... Let's go outside, then." She suggested, uncertain about all this now. She got that feeling Dipper did.
Dipper was looking down on them, confused. "Uh, guys, I'm right here... Guys?"
But they couldn't see him, for some odd reason.