In Venezuela, an offshore earthquake causes the opening of a canyon that swallows up Angel Fall's Churum River which then disappears into a large cave. At the rear of the cave, the river disappears into an abyss that is speculated to be over twenty five hundred feet deep. The existence of this abyss is brought to the attention of a group of spelunkers, aka cavers, from Austin, Texas. Exploring deep difficult caves is what these people do; it is what they live for. The leader of the group organizes an expedition to explore the cave and their primary mission is to be the first to rappel into this monster underground pit. Accomplishing this would be a monumental caving first, and they are extremely excited about the prospect. They notice that the cave walls are extremely smooth and unusual, and they speculate that something unnatural was behind the formation of the cave. As they overcome massive difficulties and near success, they encounter something that they could never have expected. This discovery changes the direction of their expedition, imperils all of their lives, and sends them scurrying on an extended trek that takes them from Venezuela to one of the most remote islands in the far arctic north.