Deep in the Yucatan jungle a newly-discovered silver mine is experiencing the bloody attacks and deadly depredations of a mysterious creature known to the locals as "El Demonio de Agua" - The Water Demon. Desperate for relief, the owners of the mining operation hire cowboy and hunter J. Everett Earl to travel deep into the dark jungle, find the creature and put an end to its reign of terror. But little does Earl know that this job entails more than a simple hunt, before he's done, the man will come to know the terrors of the spirit world as well as experiencing the ancient powers of a deformed Indian shaman called The Spider!