In 1559, forty-nine Spaniards exploring a tributary of the Orinoco River reached a sheer-sided, cloud-capped mountain called Tepui Zupay.  When they tried to climb it, all but six of them were slaughtered by Amazons.  Or so claimed Friar Sylvestre, the expedition’s chronicler.  But Sylvestre made many bizarre claims: rivers of blood, plants that lead to gold.

Jerry Pace, a burn-scarred botanist struggling for tenure at UCLA, thinks the friar was high on mushrooms.  Jerry’s best friend, the historian who has just acquired Sylvestre’s journal, disagrees.  He plans to retrace the expedition’s footsteps, and wants Jerry to come with him.  Jerry refuses, until he spots a stain between the journal’s pages — a stain left by a plant that died out with the dinosaurs.  He has to find that plant.  And when the patron who funded the journal’s purchase sends a seductive blond to accompany them, Jerry’s interest heats up even higher.

But the Venezuelan wilderness does not forgive intruders.  Their canoe capsizes, they lose their gear, a deranged Dutchman vows to slit their throats.  And their trip has just begun.  Battered and broken, they reach a remote Catholic orphanage, where the old prioress warns of death awaiting any who would venture farther.  But an exotic Indian girl leads them on, through piranha-infested rivers and jungles teaming with poisonous plants, to Tepui Zupay — the forbidden mountain no outsider has set eyes on since the Spaniards met their doom.