"I never meant to lie to them. But when the price of truth is someone you love... you learn to lie really well." When the Pines twins return to Gravity Falls for one last summer before real life begins, they expect mystery. They don't expect Elowen Wrenmoor-a quiet, clever librarian with eyes full of secrets and a smile that never quite reaches her eyes. She's hiding something. Something ancient. Something dangerous. Something shaped like a triangle and stitched into her thoughts like a second heartbeat. Because Elowen made a deal. And Bill Cipher always collects. He has her twin brother. And unless she plays along-pretends to be their friend, earns their trust, and delivers them into Cipher's trap-she'll lose Ezra forever. But the closer she gets to Dipper and Mabel, the harder it is to lie. The harder it is to stay distant. And the harder it is to ignore the voice in her head that whispers: "You were never going to save them."

Down deep in the midst of mystery and wonder lies a place few have seen. A place where frogs sing reveries of beauty and lost pilgrims. A place where children go to play and wayward souls go to wander. A mysterious place, called the Unknown. Where long-forgotten wishes wipe away canon endings and bring forth better, darker and more emotional adventures than ever before.