Deep in the heart of the darkest region of the Congo, near the legendary ruins of the Lost City of Zinj, an eight-person field expedition dies mysteriously and brutally in a matter of minutes.

Ten thousand miles away, at the Houston-based Earth Resources Technology Services, Inc., supervisor Karen Ross—watches a gruesome video transmission of that ill-fated team: a camp destroyed, tents crushed and torn, equipment scattered in the mud alongside bodies…and the grainy, moving image of a dark, blurred shape.

In San Francisco, primatologist Peter Elliot works with Amy, an extraordinary gorilla with a 620 “sign” vocabulary and a fondness for finger painting. Her recent drawing matches, with stunning accuracy, the frayed, brittle pages of a Portuguese print dating back to 1642…a drawing of the ancient lost city.

Immediately, a new expedition is sent into the Congo, descending into a secret world where the only way out may be through the grisliest death…