Reverse Falls

Basically, this is my own take on 'Reverse Falls' one of the AUs for Gravity Falls.
Here we go!

Chapter 1- Tourist Trapped PART 1
Pacifica Northwest got onto the bus with her freind, Gideon. "I can't WAIT to go to Gravity Falls!" Pacifica said, with a big smile. "You've said that for the past hour!" Gideon sighed. "I know! Im just VERY excited!" Pacifica's smile seemed to make Gideon relaxed. "If ya say so." Gideon said.

Darn Fabulous Timeskip brought to you by Mabel Gleeful!

Pacifica and Gideon got off the bus. They looked around, they couldn't find their great uncle's home. "Drat....where could it be?" Gideon muttered just as a red car pulled up. "Get in!" The man at the wheel said.

Here's a some Ceaser cipher
Tbizljb ql Obsbopb Cxiip
HINT: THREE LETTERS BACK