Six tourists hire an extreme tour guide who takes them to the abandoned city Pripyat, the former home to the workers of the Chernobyl nuclear reactor. During their exploration, they soon discover they are not alone.

There is an abandoned place nestled deep in Appalachian country where underground coal mines have been ablaze for decades. When a team of researchers try to find out how the fires started, they soon discover something more startling than the mystery that sent them there: they're not alone.