Pausing for a moment, you wipe the sweat from your brow. It's a hot day, and the jungle forest is quite humid. The path, if it could be really called a path, is quite difficult to follow. Twice already you've come to a dead end and had to double back. But the allure of what's at the end of the path is too strong to resist. It's a cave. A new cave. And, by the sound of it, a very deep cave.
You've been vacationing for several weeks in Brazil, staying in hostels, touring the countryside, when an online newsgroup you follow called out that what appeared to be a new cave was discovered by a survey team searching for possible oil deposits. The survey team only briefly examined the entrance, noting that the walls were very smooth and no end could be immediately seen. They left it at that, but you did not. The cave was sighted 12 miles west of the village you were staying in, meaning you'd be able to reach it quicker than any professional spelunker. You've been an avid cave explorer for several years, and the opportunity is just too good to pass up. Going to a store where you grabbed some rope, extra water and food, along with some tools to serve as makeshift climbing gear, you headed out early the next morning after learning where the survey team had entered the forest.
Now, pausing at the entrance of the cave, you make note of the GPS coordinates and drop your pack to take a quick break. The air coming out of the cave is cool and moist, meaning that there's probably water nearby. It might be a shaft to leads to a flooded chamber and nothing more, but at least you'll be the one to say you explored it first!
Taking a few steps inside, you feel the smooth stone interior. The cave walls are almost impossibly smooth. But you don't have time to dwell on this. From deeper within the cave, a sound echoes across the walls toward you. You hear the sound of someone screaming.