After a robbery goes wrong, teenagers Thum and Bas flee from police and find themselves in Dan Sai, a small town in Loei province where the locals are celebrating the masked procession Phi Ta Khon. It's a time when spirits are free to walk amongst the living.
Five carpoolers travel in a motorhome to reach a common destination. Night falls, and to avoid a dead animal carcass, they crash into a tree. When they come to their senses, they find themselves in the middle of nowhere. The road they were traveling on has disappeared and there is only a dense, impenetrable forest and a wooden house in the middle of a clearing, which they discover is the home of a spine-chilling cult.