Nick Cutter is an evolutionary zoologist who finds himself confronted with the subject of his studies in a way he could never have imagined. Prompted by the enthusiasm of his geeky but brilliant graduate student Connor Temple, Professor Cutter and his lab technician Stephen Hart investigate mysterious animal sightings in the Forest of Dean.

Abby Maitland, a zoo animal handler, discovers the strangest pet she’s ever seen. Could a small lizard, picked up by a young boy in the woods, really be an entirely new species? Determined to find out more, Abby and the boy head off.

Cutter invites Claudia along to join the search for the phantom beast. In the woods, they find a petrified Abby face-to-face with a Scutosaurus, a giant beast straight from the Permian Period—250 million years ago. But this creature seems to be the least of their worries. The Scutosaurus is vegetarian … so who or what hauled a dead cow high into a tree?

The young boy’s stories confirm Cutter’s worst fears: A savage Gorgonopsid, one of the Permian’s most dangerous predators, is also on the loose. He must track the beast—before it finds its next meal.

But where on earth are these creatures coming from? Are they an evolutionary throwback? Or perhaps experimental hybrids? As the Cutter and company follow the Scutosaurus, the creature inadvertently leads the team to the answer: a shimmering distortion in the air, into which the Scut completely disappears.

Could they really be looking at a rip in time-an anomaly-that leads back to prehistoric times? Can creatures come through from their own era into ours, and if so, can humans go the other way? There’s only one way to find out. Cutter is determined to make the trip, convinced that the answer to his wife’s disappearance lies on the other side.