Chris C.J. Thomason, Scott Devon Graye, Johnny Ben Easter, Brian Wes Chatham and his girlfriend Natalie Tammin Sursok are driving through rural Nebraska when a flock of crows attacks their SUV, hurling the vehicle into a crash and leaving everyone unconscious. When they come to, Johnny is missing, so Natalie and Chris stay with the battered car while Brian and Scott venture into a nearby cornfield in search of him. In the field they spot a scarecrow mounted in a clearing and a rusted, derelict car whose windshield is smeared with crow carcasses. They reach a house that looks abandoned and decaying, yet a light glows from an upstairs window, hinting at a presence still alive inside.
At the car, Natalie sees a young boy run into the cornfield and chases him, only to stumble upon a foul-smelling scarecrow at the field’s edge. She discovers human remains under the scarecrow’s clothes and hurries into the field to find Brian. Brian and Scott enter the lit upstairs room and discover a mutilated, undead Johnny sewing pieces of burlap together at an antique machine. Johnny suddenly stops, and the room plunges into darkness just as Natalie’s scream echoes from outside. Chris, who has followed Natalie, witnesses her being attacked and dragged into the corn. Brian runs outside and into the cornfield, where he and Chris eventually find Natalie’s lifeless body strung up in the clearing. Chris flees in terror after seeing a strange force enter Natalie’s eyes. Brian spots movement in the corn and tackles the “murderer,” only to realize it is a lifeless scarecrow. A second scarecrow attacks him, stabbing his shoulder, and it drags the defeated one away as Brian staggers back toward the house.
Back at the house, Brian blames Chris for not helping Natalie, and the two of them leave Scott alone to search the yard for a way out. Upon entering the barn, Scott experiences a stark hallucinatory vision of a farmer physically abusing his teenage son Corey in front of his other “favorite” son Alex, a vision Brian does not share. In the house, Brian is lured to the sewing room by the young boy Natalie had seen. An undead Natalie walks in and begins to sew a scarecrow mask. Chris tries to leave, but the door is stuck. Hearing his cries for help, Scott and Brian attempt to pry the door open, but to no avail. Chris manages to escape through the window, but falls and is knocked unconscious. Brian eventually enters the sewing room, only to find it empty.
Later, Scott hallucinates again, this time lured by Corey into the cornfield, where he witnesses Corey kill Alex in a jealous rage with a pitchfork, then dress his body as a scarecrow and leave it in the cornfield, his blood seeping into the ground. Scott wakes in the clearing to find a scarecrow emerging and attacking him, its nailed hands tearing at him before Brian smashes its head with an axe. He helps Scott back to the house, where Chris admits that he and Natalie also saw a young boy. While Brian searches the house, Chris tries to persuade Scott that Brian is unstable and that they should leave together in the truck found in the barn. Scott refuses and goes to find Brian in the house instead.
In the cellar, Scott and Brian uncover Corey’s remains clutching a shotgun, indicating Corey died by suicide. Outside, Chris hot-wires the truck and drives through the cornfield, only to be ambushed by several scarecrows. Brian saves him, armed with Corey’s shotgun, but is killed by Natalie—the scarecrow—when he cannot bring himself to shoot her. Chris returns to the house where Scott has deduced that Alex is the spirit haunting the cornfield, and that the field is only safely inhabited when Alex possesses a new body—currently upstairs sewing a mask, since he can only occupy one body at a time. While Alex occupies Brian, Chris and Scott plan to burn down the field with gasoline from the cars. But Alex finishes first and launches a full assault with numerous scarecrows. Chris kills several scarecrows with the shotgun, and he and Scott decide to split up to improve their chances of survival.
As Chris makes his way toward the road, he is attacked by a scarecrow version of Brian and impaled on a fence post, tearing Brian’s mask in two and breaking Alex’s hold over him, only to hear another scarecrow closing in. Scott attempts to ignite the field, but Alex’s original scarecrow knocks him unconscious. Scott awakens in the clearing, where Alex has mounted Chris on a scaffold. Remembering his vision, Scott finds the pitchfork used to kill Alex and stabs him repeatedly. When Alex rises again, Chris grabs him, allowing Scott to escape. Alex kills Chris and chases after Scott, who runs toward the road and collapses near the SUV.
A car pulls up, and a couple begins examining the vehicle, but Scott cannot shout loudly enough to draw their attention. Alex steps out from the corn, standing between the couple and Scott, then glances back at him before slipping back into the tall grass. The couple finally notices Scott and rush toward him as the credits roll, leaving his fate uncertain in the looming field of scarecrows.
