A mixed bag of mercenaries, hired by a mysterious businessman, arrive at and occupy a labyrinthine ex-WW2 bunker in an unnamed East European country. Once inside this distinctly claustrophobic subterranean outpost they discover a catatonic survivor and the remains of old Nazi science experiments, but they have woken a ghostly army of dedicated SS soldiers whose sole purpose is to retake the mini-fortress and, using extreme violence, take the mercenaries out.