"Don't worry, Sans... I'll never forget you..." Mabel and Dipper Pines are not your average twins. After arriving in Gravity Falls for the summer, they found themselves in a world of danger, that could soon be ending. Bill, an inter-dimensional being, had taken over the little town, and soon, the whole world. It seems when all hope is lost, Mabel has one idea, that could change everything, above and under ground. This, is Breaking thr Barrier, a Sequel to a Gravity Falls/ Undertale Crossover. DISCLAIMER: I DO NOT OWN GRAVITY FALLS OR UNDERTALE. THEY BELONG TO TOBY FOX AND DISNEY. I ONLY OWN MY IDEAS, AND THE IDEAS OF THIS COPY RIGHT. Before reading this book, please read "Underfalls" first. It is the first book in the series, I hope you will enjoy it as well