A series of films centre around six friends reunite for a caving expedition. Their adventure soon goes horribly wrong when a collapse traps them deep underground and they find themselves pursued by bloodthirsty creatures. As their friendships deteriorate, they find themselves in a desperate struggle to survive the creatures and each other.
After a personal tragedy, Sarah joins her friends on a caving expedition in the Appalachian Mountains. But when a rockfall traps them deep underground, their adventure turns into a nightmare. As they search for a way out, the group discovers they are not alone—lurking in the darkness are savage, cave-dwelling creatures. With rising tension and dwindling trust, the women must fight to survive against both the predators and each other.
Distraught, confused, and half-wild with fear, Sarah Carter emerges alone from the Appalachian cave system where she encountered unspeakable terrors. Unable to plausibly explain to the authorities what happened - or why she's covered in her friends' blood - Sarah is forced back to the subterranean depths to help locate her five missing companions.
