A skilled kayaker is working for an expedition, financed by a university, trying to find traces of a couple of Indian cultures that are rumored to have lived in the general area some years ago.
Unfortunately, the expedition head dies of a heart attack. He's replaced by a young female graduate who has it piled higher and deeper.
The kayaker would have walked away from the project, except that he has certain incentive based bonuses built into his contract. He manages to make all of his bonuses, save one remaining plum.
The new head of the project then wants the kayaker to kayak up a stream and find the temple. She wants him to do the search despite the fact that there's a several hundred foot cliff to be climbed along the course of the stream.
The villagers did climb the cliff, but they tell the kayaker that it was very, very difficult to the point of almost impossible. The villagers trek through the jungle with basically just a rifle and a machete. There's no way the kayaker is going to climb the cliff that the villagers describe with a kayak and supplies strapped to his back.
Trying to talk to the witch is something like trying to talk to a tiger. The tiger doesn't understand what you say, doesn't care what you are saying and may claw you to death if that last proves more attractive than continuing to listen to you.
The witch finally orders him to kayak up the Western stream.
The kayaker pretends to agree with her in order to get the necessary provisions to allow him to kayak back down the Amazon and escape from the wicked witch. The kayaker then hitches a ride on a supply boat, to let him get to a point where he just might be able to reach the temple.
The kayaker then paddles up a side stream and finds a temple in the jungle.
The temple proves not to be an old Amerind structure, but instead a modern building with indications that it was built by those not of planet Earth.
Inside the temple, the kayaker finds a book that was obviously overlooked when the temple was abandoned. The book contains writing in alien and also a translation in Latin.
A Priest, further down the river translates the Latin. The Latin contains a vital warning for the people of Earth. However, the Priest believes it to be fiction.
The poor kayaker then finds himself with a vital message, that could affect the future of Earth and no way to deliver the message. What's he to do?