What would happen if something went terribly, terribly wrong that fateful night in the Mystery Shack when Stan's portal was discovered? In this fic, Dipper and Mabel end up in the Unknown and meet up with Greg and Wirt, both teams of siblings trying to find their way home. This fic takes place after Not What He Seems (GF), and at the beginning of OtGW. (cover by BottleWonderland : http://bottlewonderland.deviantart.com/art/Over-the-Gravity-Falls-499261747)