As two technicians inspect the Yankee Power Company Nuclear Generating Facility, they fail to notice a leak. Soon, a nuclear dust cloud surrounds the Ravensback school bus. Driving through town, Sheriff Billy Hart finds the bus deserted on a country road with the motor running. At the nearest residence, the sheriff learns that Tommy Hill, the son of Dr. Joyce Gould’s sickly tenant, has not returned from school. When Joyce finds Tommy’s possessions still on the bus, the sheriff radios Deputy Harry Timmons to set up a roadblock at the interstate. After the sheriff leaves, Joyce hears a voice in the cemetery across the street. There, Tommy appears and hugs Joyce, who becomes desiccated and dies. At the town grocery, Sheriff Hart tells local resident John Freemont about his search, while Molly, the store owner, cannot reach bus driver Fred Mansfield on the phone. At the Shore residence, Sheriff Hart alerts Dee Dee that her nine-year-old daughter, Janet, is missing. Sometime later, John’s car breaks down, and the sheriff, who is passing by, offers him a ride. Meanwhile, schoolgirl Ellen greets her mother, who is killed by her daughter’s touch. At home, Deputy Timmons’s girl friend, Suzie MacKenzie, ignores her younger brother Paul when he silently greets her with arms extended. Paul follows Suzie into the garage and kills her. At the Freemont residence, Sheriff Hart greets John’s pregnant wife, Cathy, and explains the circumstances surrounding the school bus. Meanwhile, Molly radios Deputy Timmons and asks him to investigate the Gould house after she receives a hysterical call from tenant Leslie Button. Driving there, Deputy Timmons sees three children on the road and phones Molly with the good news. As Deputy Timmons approaches the children, they stand with their arms extended. Molly radios the sheriff to announce that the children have been found near the Gould place, so Sheriff Hart and John drive over to see them. However, they find Deputy Timmons dead on the side of the road and the children are missing. At the Gould residence, they discover Leslie’s desiccated body along with her dead dog, and drive to Molly’s grocery to get help. In the store, Sheriff Hart tells Molly that Deputy Timmons and Leslie were mutilated and killed. The men grab rifles and bullets from the wall rack, race back to the Fremont residence and find Janet standing in the middle of the road. They question her, but she is unresponsive. At Janet’s house, John finds the mutilated bodies of Janet’s parents by the pool in the backyard. Janet tries to attack Sheriff Hart while she sits in the back seat of the squad car. He eludes her grasp and she disappears. In a panic, the men drive to the Fremont house as Molly radios that the schoolchildren are at the store. When Molly greets them, they attack her and the sheriff hears her screams over the radio. At the Fremont residence, Cathy is safe, but John is afraid to tell her any details about the deaths. While making coffee in the kitchen, Cathy sees their daughter, Jenny, outside the house, but the men prevent her from touching her daughter. Sheriff Hart and John follow Jenny to the barn, where she burns her father’s hand with her grasp. The sheriff shoots at Jenny and Janet, who appear out of the shadows, and the men escape to the main house, but as the schoolchildren approach, Sheriff Hart discovers his bullets cannot kill them. When Cathy sees Sheriff Hart shooting children, she is horrified and knocks him unconscious. Cathy does not want to believe that Jenny mutilated John’s hand and runs upstairs when she hears noises in her son Clarkie’s bedroom, but she is too late. Clarkie has opened his bedroom window for Paul, who kills him. Paul follows Cathy down the staircase and backs her into a corner. Just before he touches her, Sheriff Hart cuts off Paul’s hands at the wrist with a sword, killing him. When Janet appears at the front door, John chops off her hand with the sword. While Hart and John search outside for the other children, Cathy remains in the house. The men follow the children to the barn, killing them with an axe and the sword. As Sheriff Hart uses the radio in the squad car, Janet rises up from the back seat and kills him. John hears the sheriff’s screams, stumbles over to Janet and hacks her to pieces. He pulls Sheriff Hart’s limp body out of the car and cries for his dead friend. Suddenly, John hears Cathy cry as she goes into labor. When the baby is born, John stares at the black nails on the child’s hands and realizes that it, too, has been afflicted and will become a monster.