Even though he's secretly terrified of deep water and all the scary things that swim below, Tate wants to shake his boring reputation, so he agrees to travel with his class up the Amazon River to help build a village school. He has his fingers and toes crossed that he won't see any giant snakes or hungry piranhas.

But there are even scarier things than anacondas lurking in the jungles of South America, and Tate soon learns of the legend of El Tunchi, a vengeful spirit that terrorizes those who harm the rainforest. When creepy things start happening and Tate keeps hearing El Tunchi's haunting whistle, he's sure the group must have angered someone. Or something. He and his friends need to figure out a way to make amends and get out of the jungle alive.