A joint Thai-American company builds a bridge across the Mekong River. Construction works disturbed the ancient inhabitant of those waters, namely the Serpent, which began to kill the workers. Dave Chon, at the request of the head of the company, comes to the site and tries to understand the situation. He helps Kim, who is doing research in that area. They go on an expedition to the Mekong, where they find a tribe living alone. Residents of the tribe told that the Serpent lives in a cave and protects treasures. This was learned by the military, who also equipped their expedition. As a result of their actions, the entrance through the caves to the tribe was blown up and Kim stayed there. Dave, completing the bridge and with hope in his heart, went in search of Kim. At the entrance to the cave, he encounters the Serpent. Will the ancient deity answer the pleas of Dave for help?