When a cataclysmic explosion devastates New York, eight strangers take refuse in the basement of their apartment building, a converted fallout shelter. The shelter suddenly comes under attack by men in Hazmat suits forcing the strangers to join forces in a desperate bid to take on the new enemy. Amid the chaos there is no real understanding of what these Hazmats are looking for and what drives them to be so merciless. Their sanctuary becomes a living hell where the survivors must use their wits to save themselves from becoming victims of the pack in a thrilling and gut wrenching finale.