In the corn farming community of Gatlin, Nebraska, a nefarious boy preacher named Isaac believes he is the human intermediary of an all-powerful, demonic deity called “He Who Walks Behind the Rows.” Isaac, and his lieutenant, Malachai, brainwash the town’s children into carrying out a daylong massacre, killing everyone over nineteen years of age. Witnessing the killing, an adolescent named Job remains secretly defiant of the cult. He protects his prescient sister, Sarah, who draws pictures of future slayings. Three years after the bloodbath, a young couple happens upon Gatlin on a road trip to Seattle, Washington. Burt, a recent medical school graduate, has won an internship at a Seattle hospital and his doting girl friend, Vicky, is joining him on the journey in the hope he will one day commit to family life. As they lose their way in the cornfields, the car collides with a boy named Joseph, and Burt is startled to discover that his throat was slashed before the accident occurred. Unbeknown to Burt and Vicky, the adolescent was killed by Malachai when he attempted to escape Gatlin. Burt is eager to report the murder and proceeds to town, despite reproval from the last remaining adult in the area, an elderly mechanic named Diehl. Meanwhile, preacher Isaac warns his disciples about the arrival of “Outlanders” and orders them to kill the intruders. In town, Burt and Vicky creep into the abandoned Hanson’s Café, where the massacre began three years earlier, and are alarmed when several children try to steal their car. As the youths run away, Burt and Vicky give chase and stop at a farmhouse. There, they find Sarah, who cryptically explains that her cult leader, Isaac, has banished the adults to the cornfield. Failing to realize the townspeople were murdered, Burt is convinced Gatlin is safe and returns to town. Vicky stays behind and learns that music and art have been prohibited. She encourages Sarah to draw and is disturbed by her portrait, which depicts Vicky as the victim of a cornfield massacre. Just then, Isaac’s young disciples surround the house with scythes and take Vicky to the cornfield, where she is suspended from a cornhusk crucifix. Although Malachai has procured one of the “Outlanders” as ordered, Isaac complains that his henchman’s bloodlust is compromising their covenant with “He Who Walks Behind the Rows.” Isaac believes Malachai displeased the deity by failing to perform a sacrificial ritual when he killed young Joseph, and by murdering the mechanic, Diehl, after he spoke with the “Outlanders.” Diehl was kept alive because he provided the community with its only source of fuel, and now the town will struggle to survive. Isaac hopes to appease the demon by sacrificing the “Outlanders,” and orders Malachai to detain Burt. Elsewhere, Burt realizes the town has been taken over by murderous zealots and races back to the house. Sarah remains mum about Vicky’s disappearance, but her drawing leads Burt to the cornfield. However, he is distracted by the sound of church bells and runs to the chapel where Rachel, a knife-wielding priestess, carves a pentagram into the chest of an ecstatic teenaged boy named Amos. Using his blood as ink, she adds his name to a list of teenagers that have been sacrificed to “He Who Walks Behind the Rows” on their nineteenth birthdays. As Burt protests, Rachel attacks, but he seizes her knife and escapes. Although Malachai gives chase, Burt defends himself with the blade and is rescued by Sarah’s older brother, Job. The boy hides Burt in a nuclear fallout shelter built by his father and tells him the story of the Gatlin bloodbath. Back in the cornfield, Malachai commandeers Isaac’s authority, ordering the disciples to release Vicky from the crucifix and replace her with Isaac. Holding Vicky at knife-point, Malachai returns to town, hoping her screams will convince Burt to come out of hiding, but Burt cannot hear her from the underground shelter. At nightfall, Job and Sarah lead Burt to the cornfield. As Malachai continues to hold Vicky hostage and prepares for Amos and Isaac’s sacrifice, the supernatural fury of “He Who Walks Behind the Rows” manifests itself in an invisible underground force that tunnels through the earth. When Isaac is consumed in bright light and beamed into the stormy sky, Burt begs the children to question their faith. Malachai attacks, but the youths ignore his orders to fight. Just then, Malachai’s first victim, Joseph, is resurrected from the dead, possessed by “He Who Walks Behind the Rows.” Speaking in the demon’s voice, Joseph declares that he must sacrifice Malachai, and chokes the boy to death. The terrified children take shelter in a barn, and Burt is finally reunited with Vicky. However, the storm worsens, and the building is near collapse. As Burt struggles to plot their escape, Job remembers that a police officer named Sheriff Hotchkiss once tried to save the town by reciting a page from the Bible. Isaac told his disciples that Hotchkiss was the fearful “Blue Man,” and had him crucified. When Job reports that Hotchkiss had a particular interest in the town’s gasohol still, Vicky realizes that he was planning to burn the cornfield. With the help of the children, Burt attaches hoses to the gasohol still and guides the tube into the field. Job helps him connect the hose to sprinklers and they spray the field with flammable liquid. As the menacing spirit of “He Who Walks Behind the Rows” materializes in storm clouds overhead, Burt throws a burning Molotov cocktail into the cornrows, igniting an explosion. The field detonates into a mushroom cloud, and a mystical force is projected into the universe. Burt, Vicky, Job, and Sarah run away to Burt’s car and find it inoperative, so they resolve to walk nineteen miles to the nearest town. As Burt steps inside the vehicle for a map, Isaac’s surviving disciple, Rachel, jumps up from the back seat and attacks. Vicky slams the door on her head, knocking her unconscious. Burt does not wish to leave Rachel in a wounded state, but Vicky urges him to escape. With Job and Sarah in their care, the couple resumes their journey to Seattle as a newfound family.