Faith, Colorado, doesn't get many visitors. But this spring, a mysterious creature is lurking on the mountain. Fiercer than a mountain lion, it’s been hunting pets and leaving their remains scattered over the mountainside. But what is it, and what does it want? Only Rob and his best friend, Phoebe, are brave enough to investigate.

What they find on the mountain is the Last Synapsid—a squat, drooly creature that looks like a dinosaur crossed with a wienerdog—that claims to need Rob and Phoebe’s help. Having wandered into a time snag from his own era, 30 million years before the dinosaurs, “Sid” is chasing a violent carnivore called a gorgonopsid. The Gorgon has become fascinated by humanity and refuses to return to his proper place in time. But if he doesn’t, history will re-align, humans will never evolve, and Rob and Phoebe will end up as nothing more than characters in an elderly synapsid’s dream.

Timothy Mason is a playwright who wrote the book and lyrics for the Broadway musical version of How the Grinch Stole Christmas! He lives in New York. The Last Synapsid is his first novel.