Summer Clark is a newcomer to Gravity Falls, Oregon. Her parents sent her here, so she could be safe, when really she's in even more danger. When she arrived everyone was as frightened as they were 30 years ago. When a demon took over the town. One day while Summer is in the forest, she finds an abandoned tourist trap that was called, The Mystery Shack. There she finds out Gravity Falls dark past, and meets the reason for the past.

Mabel and Dipper are back in Gravity Falls with the I Gruncle Stan and Soos. But this summer someone came into Mabel's life, Billy Cummins. Dipper claims that Billy is working for Bill Cipher the triangle that entered Stan's mind. Mabel doesn't believe him. But what happens when Mabel finds out about Bill's past?

Ever since Mabel was put in jail for something she didn't do she's been slowly leaving sanity. She's been writing 'Destroy Dipper' on her jail cell walls and she's been thinking of ways to send Dipper to Hell. When she's released after ten years Mabel is on a hunt for Dipper. And to destroy him once and for all.

It's been two years since Dipper died and Mabel has been to Gravity Falls. Things have changed since then. Dipper has made an oath to Bill to take his place, but Dipper hasn't done anything Bill has done yet. He's never possessed and he's never killed anyone. Slowly Dipper slips out of sanity. Mabel is almost sixteen and she's excited, but she thinks Gravity Falls will be the same. With Gideon flirting with her more than ever, Gruncle Stan getting sick, plus the weird dreams she's veen having, things are more stressful in Gravity Falls. When Dipper keeps to himself and Mabel doesn't tell Dipper what's going on with Stan, these twins will grow more and more apart.