Katherine Winter (Hilary Swank) was previously a Christian missionary, but after her family was tragically killed, she lost her faith. Now she has become a world renowned expert in disproving various religious phenomena with her sidekick Ben (Idris Elba). Her latest investigation takes her to a small town called Haven, where the river has turned red with blood and the townspeople believe that a plague is coming and believe it is being caused by a 12 year-old girl (AnnaSophia Robb).