In the middle of a routine patrol, officer Daniel Carter happens upon a blood-soaked figure limping down a deserted stretch of road. He rushes the young man to a nearby rural hospital staffed by a skeleton crew, only to discover that patients and personnel are transforming into something inhuman. As the horror intensifies, Carter leads the other survivors on a hellish voyage into the subterranean depths of the hospital in a desperate bid to end the nightmare before it's too late.

故事发生在一座小镇的医院内。一名警官将一位伤员送进医院后，一群身份不明的神秘人包围了医院。宗教？黑帮？恐怖组织？在知晓这群人的身份之前，一场大屠杀已经展开。