In 1963, the town of Gatlin, Nebraska, is suffering a severe drought. In a tent, a boy preacher (Robert Gerdisch), claims that an Old Testament-era Canaanite god whom he calls “He Who Walks Behind the Rows” has spoken to him in his dreams. He tells the other children that the sinful adults are the reason for the drought, prompting them to kill everybody over the age of nineteen in town. They then establish a death cult with the prime rule that, upon reaching the age of nineteen, one must be sacrificed to the cult’s god.
Twelve years later, a bickering couple, Vietnam veteran Burt (David Anders) and his wife Vicky (Kandyse McClure), are driving near Gatlin, planning their second honeymoon, when a boy named Joseph (Remington Jennings) stumbles out of the roadside corn in front of their car. After running Joseph over, Burt realizes the boy’s throat was slashed. Wrapping and placing the body in the trunk, Burt tells Vicky to wait for him while he looks around. In the cornfield, Burt finds Joseph’s bloodied suitcase. He and Vicky drive off in search of aid, not realizing they are being watched by Isaac (Preston Bailey), the 9-year-old current cult leader, and 18-year-old warrior Malachai (Daniel Newman).
After hearing a group of children giving an evangelical sermon over the radio, Burt and Vicky reach an abandoned gas station. Finding the phones non-functional Burt decides to go to Gatlin. While Burt drives, Vicky finds an amulet which she recognizes as a pagan creation. Meanwhile, in the cornfields, Isaac tells the others about Burt and Vicky and that they, like the “blue man” (a police officer who was crucified for trying to stop them) must be killed to appease “He Who Walks Behind the Rows”, who demanded Joseph be killed for trying to escape.
Reaching the town, Burt and Vicky find it seemingly abandoned, with a calendar in a bar still reading 1963. Coming across a church with a sermon board dated last week, Burt goes in to investigate, ignoring Vicky’s pleas that they should just leave. Inside the church, Burt finds various occult drawings, a larger version of the trinket in Joseph’s suitcase and a book listing the birthdays of the town’s inhabitants.
As Burt reads the book, Vicky is surrounded and attacked by Malachai and several other boys. She manages to kill one of them with Burt’s shotgun before Malachai stabs her. Burt rushes outside just as Malachai blows the car up. Chased by the children into an alleyway Burt is taunted by Isaac who throws a knife at him which hits him in the arm. Killing two of the older boys, Burt runs off into the cornfields.
In the alleyway, Isaac confronts Malachai, telling him that by spilling Joseph’s blood in the corn he angered He Who Walks Behind The Rows. Questioning Malachai’s faith, Isaac has him pray before they regroup with their followers, who they tell must sacrifice Burt in the clearing where the blue man’s corpse is held. Malachai and the children begin hunting Burt through the corn.
Malachai is told by Nahum (Paul Butler, Jr.), one of the younger boys, that he had a vision of He Who Walks Behind the Rows, leading Malachai to believe Nahum will be the new prophet after Isaac. Malachai mentions that they must finish the search before dark, as that is He Who Walks Behind the Row’s time.
Burt begins having flashbacks to Vietnam and kills several of the children, including Nahum. At nightfall the worshipers abandon the search and return to the town. They have a feast prepared by the females, who seem concerned that Burt was not apprehended. Later that night, Isaac holds a sermon in the church based on the tenet of “be fruitful and multiply” and proclaims that the time of fertilization has come. He beckons a teenage girl (Zita Vass) and boy (Jake White) up to the front of the church and they immediately disrobe and have sex in front of the entire congregation.
Burt, lost and delusional, has visions of all those he has killed, and begins wandering around aimlessly, searching for the road as the plant life begins attacking him. He finds the clearing and discovers Vicky, who has been made into a scarecrow. Hallucinating that Vicky’s body is talking to him, Burt is faced by He Who Walks Behind The Rows, who proceeds to disembowel him and rip his eyes out in a form of ritual sacrifice.
The next day, Isaac tells the children that He Who Walks Behind The Rows is displeased with their inability to kill Burt, who He had to dispose of Himself—like the blue man (who, when killed, reduced the ‘age of favor’ from twenty to nineteen). Isaac informs everyone that the age of sacrifice has been lowered from nineteen to eighteen as punishment for their failure. After the children leave Isaac stands in front of a pile of the children’s bodies and as he sets them on fire shouts “Scarecrow!”. The scarecrow is revealed to be Burt.
Later, Malachai and the other eighteen-year-olds enter the cornfields at dusk, offering themselves to He Who Walks Behind the Rows. While saying goodbye, Malachai’s pregnant lover Ruth (Alexa Nikolas), whose faith had earlier been shaken, has a vision of herself setting fire to the corn.