Deep in Yellowstone's Thorofare—one of the most remote places in the lower 48—a biologist named Jason Hollows was tracking what he believed to be a new apex predator. But the claw marks were too precise. The patterns too organized. As Jason hiked deeper into the wilderness, he uncovered something older than the park itself—something human, but long forgotten by civilization.

This is the story of what he found, and how he barely made it back.