In Bridgton, Maine, artist David Drayton, his wife Stephanie, and their eight-year-old son Billy take shelter in the basement of their lakeside home during a severe thunderstorm. While surveying the damage the next morning, they notice a thick mist advancing over the lake. David and Billy leave for town with their neighbor Brent Norton to buy supplies.
Inside the supermarket, they watch police cars speed down the street, and a terrified civilian, Dan Miller, runs into the store and warns of a danger lurking in the mist. As a siren sounds, store managers Ollie Weeks and Bud Brown close off the supermarket, and the mist envelops the store. Against David's advice, bagger Norm goes outside to fix the store's emergency generator, but he is grabbed by a tentacled creature and dragged into the mist. David and Ollie direct the customers to barricade the storefront windows, but one woman leaves to go home to her children. Mrs. Carmody, a religious fanatic, begins preaching about an impending Armageddon, while a small group of skeptics led by Brent leave the store to seek outside help, which results in their deaths.
David forms connections with several people in the store, including Amanda Dunfrey and Irene Reppler, two teachers who came into conflict with Mrs. Carmody over her religious zealotry. Amanda carries a revolver in her purse, and gives it to Ollie, who is a former regional shooting champion. As night falls, enormous flying insects – attracted to the lights – swarm in front of the store and are preyed on by pterodactyl-like creatures. One of the creatures smashes a window, allowing the insects inside. In the ensuing panic, two people are killed and another is burned to death in an attempt to incinerate the insects. Meanwhile, Mrs. Carmody is miraculously spared from an insect, leading her to proselytize more fervently and gain followers among the survivors.
A small group led by David goes to the neighboring pharmacy in search of medical supplies, but is attacked by giant spiders that kill two men, forcing them to retreat. Mrs. Carmody, who had opposed the expedition, uses this failure to increase her influence by offering protection from divine wrath to new converts. The next day, following the suicides of two soldiers from the local military base, a third soldier, Jessup, reveals that a government project to discover other dimensions was underway at the base, and that scientists may have opened a doorway into a dimension containing the creatures invading the town. Mrs. Carmody's followers offer Jessup as a sacrifice and expel him from the supermarket, and he is immediately devoured by a giant praying mantis-like creature.
The next morning, David and his group prepare to leave the store, but are stopped by Mrs. Carmody, who demands that Billy be delivered as the next sacrifice. Ollie, however, guns her down, then threatens her traumatized followers into standing down, thus allowing the group to escape. Outside, he and two others are devoured by the creatures, while Bud runs back to the store, while David, Billy, Dan, Amanda, and Irene reach David's car.
Driving through the mist, David finds his home destroyed and Stephanie dead. Devastated, he drives away from town, passing a colossal six-legged beast and eventually running out of gas. With no means of escaping the mist, the resigned group members decide to end their lives. David shoots Billy and the other three survivors with his four remaining bullets before leaving the car to be taken by the creatures. The mist suddenly dissipates, revealing the vanguard of a U.S. Army armored column that is in the process of exterminating the creatures and restoring order. Seeing that they have also rescued those from the store, including the woman who left to get to her kids, David realizes that he killed his son and friends for nothing, and drops to his knees screaming.
Thomas Jane as David Drayton, a painter who ends up trapped in the supermarket with his son Billy
Marcia Gay Harden as Mrs. Carmody, a religious fanatic who believes the mist to be the wrath of God
Laurie Holden as Amanda Dunfrey, a new teacher at the local school. She carries a Colt revolver with her at all times
Andre Braugher as Brent Norton, a big-city attorney and David's neighbor
Toby Jones as Ollie Weeks, the supermarket's assistant manager, who is experienced with guns
William Sadler as Jim Grondin, a belligerent and weak-minded mechanic
Jeffrey DeMunn as Dan Miller, who takes shelter in the market after witnessing the dangers from the mist
Frances Sternhagen as Irene Reppler, an elderly teacher and Amanda's co-worker
Alexa Davalos as Sally, a cashier at the supermarket and Billy's babysitter
Nathan Gamble as Billy Drayton, David's eight-year-old son
Chris Owen as Norm, a bag boy
Sam Witwer as Private Wayne Jessup, a soldier stationed at the nearby Arrowhead military base
Robert Treveiler as Bud Brown, the supermarket's manager
David Jensen as Myron LaFleur, a mechanic who works with Jim
Melissa McBride as an unnamed woman who left her kids alone at home
Andy Stahl as Mike Hatlen, one of the patrons at the supermarket who side with David's group
Buck Taylor as Ambrose Cornell, a mustached man who sides with David's group and has a shotgun in his truck
Juan Gabriel Pareja as Morales, another soldier from Arrowhead base
Walter Fauntleroy as Donaldson, another soldier from Arrowhead base
Brandon O'Dell as Bobby Eagleton, Joe's brother and one of the patrons at the supermarket who side with David's group
Jackson Hurst as Joe Eagleton, Bobby's brother, who tries to build a torch with a mop, but fails
Susan Watkins as Hattie Turman, a local real estate agent
Mathew Greer as Silas, one of the patrons at the supermarket who sides with Brent's group
Kelly Collins Lintz as Stephanie Drayton, David's wife and Billy's mother
Ron Clinton Smith as Mr. Mackey, the supermarket's butcher
also known as Stephen King's The Mist
based on the 1980 novella "The Mist" by Stephen King