John Sayers is a storm researcher determined to crack the mystery of the violent weather that is ravaging his home state of South Dakota. After a failed test of his new tracking system, he encounters Madeline Kinney, a cult researcher who is pursuing a nefarious "church doctor" through a string of several small Midwestern towns. He dismisses her efforts until she reveals the church doctor may have taken the life of his friend. As John perfects his system to predict the path of the next tornado, Madeline tries to rescue others from the spreading influence of the church doctor. Together they discover hidden forces at work in the sky and on the ground that culminate in a revival like no other.