21 parts Complete A group of archaeology students sets out to explore a mesa in Colorado known as "Hellmouth", hoping to find the legendary City of Gold allegedly built by the ancestral Puebloans. The mesa is closed to tourists and explorers and has a dark history of hundreds of people disappearing without a trace over the past centuries.
The group takes horses to reach the remote location, far away from civilization, without any contact with the outside world. While sheltering from a storm in a small cave at night, a landslide blocks the entrance, locking the group in and forcing them to go further inside in search of another exit.
However, they soon realize that they are not alone in the darkness and that some caves should never be entered...
