The senior pupils of St Peter's High School are on retreat to a secluded outdoor activity centre, coming to terms with the murder of a fellow pupil through the means you would expect: counselling, contemplation, candid discussion and even prayer - not to mention booze, drugs, clandestine liaisons and as much partying as they can get away with.
Not so far away, the commanders of a top-secret military experiment, long-since spiralled out of control, fear they may have literally unleashed the forces of Hell.