David Drayton drove to the supermarket the day after a devastating rainstorm to get supplies for removing a fallen tree from his backyard and fixing some broken windows. He arrived at the market with his son Billy and his neighbor Brent Norton, and saw the mysterious green mist start to appear. Once the mist completely engulfs the store he tries to get a blanket for his shocked son Billy but hears and smells something strange. After Ollie, the assistant manager, Norm the bag boy and two mechanics from the town, Jim and Myron travel down to the loading dock he sees the first of the creatures from the mist. Tentacles slither into the loading dock and grab Norm. The tentacles begin to pull Norm outside as David tries to pull him back in. He eventually lets him go when he sees he can't save him. After losing his temper and beating Myron for convincing Norm to go outside, he eventually stops and walks back upstairs with Ollie. Once the remaining men head back up stairs David tries to convince everyone in the market about the danger outside. After the survivors break into two groups, David sides with Dan Miller and Mike Hatlin's group, and tries to keep Norton from going into the mist with the rest of his group. David ties a rope around one of the men, and proves the true dangers of the mist when Norton is killed. At night, enormous flying insects land on the windows and pterodactyl-like animals prey on them, eventually causing the glass to break. The breach allows some of the creatures to wreak havoc inside the grocery store. Two people are killed, and one is badly burned. Mrs. Carmody is spared by one of the insects when she prays. She starts preaching and quickly gains followers among the distraught survivors. David and a group of volunteers attempt to retrieve medical supplies for the burnt victim from the pharmacy. The pharmacy appears to be empty, but its patrons have been ensnared in webs. David's party also discovers an MP who has been webbed to a pillar. The MP gasps that the mist was "their fault." David's party is then attacked by dozens of otherworldly spider-like monsters. Two members are killed, and the surviving members flee with the supplies. Despite their efforts the burn victim still dies from his injuries. At the store, two of the soldiers have committed suicide, and the remaining soldier, Private Jessup, reveals that the local military base was filled with rumors about Project Arrowhead—an attempt to look into other dimensions, and the scientists responsible for the experiment may have inadvertently opened a doorway into a dimension containing the creatures that surround them. Mrs. Carmody whips the congregation into a killing fury, urging them to sacrifice Jessup so that the creatures will leave the rest of them alone. Jessup is repeatedly stabbed and thrown out of the store, where he is grabbed and devoured by a large praying mantis-like creature. David and a handful of rational survivors secretly gather supplies to flee. The next morning, however, they are intercepted by Mrs. Carmody, who destroys the supplies and attempts to have David and the other non-believers killed, only to be killed herself by Ollie, who threatens the rest of the cultists in turn. With the cultists returning to their senses following the death of their leader, David and his group are allowed to leave. While running to David's car, three people (including Ollie) are killed by creatures, while store manager Bud Brown is lost in the confusion and runs back to the store in a panic. The remaining members of David's group—Amanda, Irene, Dan, and Billy—make it to the car and retrieve Amanda's revolver. They drive past the store window, as Bud and the rest watch. Driving through the mist, David returns home to find his house destroyed and his wife dead. Heartbroken and in tears, he drives the group south, seeing destruction and a gigantic multi-legged, tentacled beast. After hours of traveling, they run out of gas. While Billy is sleeping, the four adults hear a monstrous sound and decide that there is no point in going on. With four bullets left in Amanda's gun and five people in the car, David shoots the other four rather than have them suffer from the beasts. Distraught and determined to die, David pulls the trigger on the handgun several times but the gun is empty. David locks himself out of the car and calls out for the monsters to come and get him. To his horror and surprise, a US Army Paladin emerges from the mist, followed by a large army unit equipped with NBC suits and flamethrowers. As the mist recedes, burning carcasses of the monsters are seen, while several truckfuls of both soldiers and survivors also pass David. Among them is the woman who left the store at the storm's outset, along with her two young children, whom she left to save. Realizing that they were only moments from being rescued and had been driving away from help the entire time, David falls to his knees, screaming, while two soldiers look on in confusion. His fate is unknown although it is likely David committed suicide.
- In the book, David has a brief affair with Amanda.
- In the book, instead of the tragic ending, David hears the word "Hartford" on the car radio. Almost out of gas, he decides to take a chance and head towards Connecticuit, their only hope. Stephen King said that the ending to the film was far better, however. He said that it was so good he wished he had thought of it.