Matt and Emily Calder’s travels through time come to a thrilling conclusion in the third book of the Hollow Earth trilogy as the siblings struggle to close Hollow Earth—and keep the monsters inside.

Twins Matt and Emily Calder may be divided by time, but they are united in their mission to close Hollow Earth before the monsters inside can destroy the world. The key to success lies with their Animare talents: they can draw things into life and travel in time through art. But there are monsters outside Hollow Earth as well. Monsters intent on taking control of the beasts for themselves. And the worst monster of all is their own father…