When the body of Hunter Gearhardt washes up on the banks of a seasonal river outside of Pomacochas, Peru, with only samples of vegetation, a handful of feathers, two black- and gray-streaked rocks, and a golden headdress of indeterminate origin in his possession, his grieving father launches an expedition to determine how his son died. The party uses these clues to divine Hunter’s route into the jungle, where they find a surviving offshoot of a primitive tribe, long thought to be extinct, and something far more sinister, something that’s been able to avoid discovery for eons for one simple reason: No one leaves the rainforest alive.