Deep in the African rain forest, near the legendary ruins of the Lost City of Zinj, an expedition of eight American geologists are mysteriously and brutally killed in a matter of minutes. Ten thousand miles away, Karen Ross, the Congo Project Supervisor, watches a gruesome video transmission of the aftermath: a camp destroyed, tents crushed and torn, equipment scattered in the mud alongside dead bodies, all motionless except for one moving image, a grainy, dark, man-shaped blur. In San Francisco, primatologist Peter Elliot works with Amy, a gorilla with an extraordinary vocabulary of 620 "signs" who likes to fingerpaint. One of her drawings match the brittle pages of a 1642 print, a drawing of an ancient lost city. A new expedition-- along with Amy-- is sent to the Congo, where they enter a secret world, and the only way out may be through a horrifying death.