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A school trip goes disastrously wrong when a visit to local caves turns into something far more sinister. Five teenagers find themselves trapped beneath the ground. Their best chance of escape is to stay together. Then a member of the group disappears, and their hopes of leaving start to fade. Does one of the remaining four know more than they are letting on, or is there something evil lurking in the caves? The five find themselves in a struggle for dominance as well as survival....