A Code to DeCipher (BillDip)

Book 1 in a 3 Book series... Dipper and Mabel Pines are back in Gravity Falls for another summer. They may be sixteen, but the thrill of the mystery is still there! For the past few weeks, Dipper has gotten little to no sleep. Ever since returning to the Mystery Shack, his dreams have been tormented by a certain dream...