"I mean, who would sacrifice everything they've worked for just for their dumb sibling?"
Mabel thought back to all the adventures that she and Dipper had had during the summer… how many times had he protected her, or given up what he'd wanted just to make her happy? How many times had he saved her, one way or another? And even before this summer, Dipper had always been there to lend her a helping hand, to support her when she most needed it.
And just like that, Mabel made her decision.
"Dipper would."
As Bill made a guttural sound of confusion, Mabel steeled herself before jumping onto the catwalk, still holding the journal firmly as she wrestled the demon who had taken over her brother's body. Bill let go of the rope as he tried to take the journal from Mabel, and the wedding cake prop fell onto the stage, crushing the puppets below and breaking into pieces. He pushed her against the metal floor of the catwalk, and the detonator that Mabel had kept in her back pocket went off, destroying her box of puppets as well as a good chunk of the theater. Spectators were running away, booing and screaming.
Her play was now well and truly ruined.
But that was all just background noise. What mattered now was keeping the journal away from Bill and finding a way to return her brother to his body. Dipper had given so much for her, over the years, and especially over the course of this strange summer… now it was Mabel's turn to return the favor.
The girl quickly gained the upper hand in the fight, still bursting with energy from her consumption of Mabel Juice, Bill occasionally stumbling as the demon struggled to remain in control of the boy's ailing body (though the scrapes and cuts gained from every stumble only made him grin wider and fight harder). Finally, Mabel was able to pin Bill against the rails of the catwalk, pushing him towards the metal guards with one hand while still holding the journal with the other, the book slightly torn and mangled from the fight but still intact.
"Give my brother his body back, you triangle monster!"
Bipper cackled before returning to his too-wide grin. "I don't think so!" The boy's body slid downwards in one fluid motion until all that remained on the catwalk were his fingers clutching its metal edge.
Mabel dropped the journal, producing a loud clang! as the book hit the metal floor of the catwalk, and reached out to Bill with both hands, trying to help him back up. The two made eye contact for a second. Those eyes were not her brother's eyes, and just looking so closely at them made the hairs on the back of her neck stand up, but it was her brother's face, her brother's body, dangling perilously to the catwalk. If saving Dipper's body meant losing the journal, it would be well worth the sacrifice.
As Mabel's heart raced, Bill extended his hand and grabbed the journal. By the time she went to clutch his arm and pull him back up, Bill was back where he had started, only the tips of his fingers preventing him from falling.
Bill winked at her.
"Looks like we've reached the end of the show!"
And he let go.
Mabel heard the crunch of his body hitting the stage and the crack of his bones breaking, but it took her several seconds before she could muster the courage to look down. Her brother's limbs were splayed out in ways that made Mabel cringe just seeing them, and his head definitely wasn't supposed to be twisted around quite that much. The journal had fallen onto the boy's upper chest and was now open to one of the first pages of the journal that the girl had ever seen, a page whose subject she could identify even from afar: it was, unmistakably, about the undead.
It took Mabel a moment to realize that the high-pitched screeching that followed was her own.
"DIPPER!"