You and your best friends Dipper and Mabel Pines are in the Mystery Shack, Mabel is being silly and sitting on a globe as it spins, Dipper is reading the 2nd journal, and you're doing whatever you choose, suddenly the ground and building starts to shake, knocking things off the shelves and counters, causing Mabel to fall to the ground off the globe

Bill Cipher is back, and wants you