The morning after a violent thunderstorm, a thick unnatural mist quickly spreads across the small town of Bridgton, Maine, reducing visibility to near-zero and concealing numerous species of bizarre creatures which viciously attack anyone and anything that ventures out into the open. The bulk of the story details the plight of a large group of people who become trapped while shopping in the town supermarket, among them a commercial artist named David Drayton (the protagonist and narrator), David's young son Billy, and their estranged neighbor Brent Norton who accompanied them into town after Brent's car was smashed by a tree. Amongst others trapped in the market are a young woman named Amanda Dumfries and two soldiers from a nearby military installation, home to what is referred to as "The Arrowhead Project". The two soldiers' eventual joint suicide lends some credence to the theory of this Project being the source of the disaster. Soon after the mist comes, something plugs the store generator's exhaust vent. When a young bag boy named Norm steps outside to fix the problem, he is pulled into the mist by a swarm of tentacles. David and Ollie Weeks, the store's assistant manager, witness Norm's death and try to convince the remaining survivors of the danger lurking outside. Norton and a small group of others refuse to believe, and are accusing David of lying. They venture out into the mist to seek help, where they are killed by a huge, unseen creature. This, along with a deadly incursion into the store by a pterosaur-like creature and a disastrous expedition to the pharmacy next door, lead to paranoia and panic consuming the remaining survivors. This spiraling breakdown leads to the rise to power of a religious zealot named Mrs. Carmody who convinces the majority of the remaining survivors that these events fulfill the biblical prophecy of the end of times, and that a human sacrifice must be made to save them from the wrath of God. David and Ollie attempt to lead their remaining allies in a covert exit from the market, but are stopped by Mrs. Carmody, who orders her followers to seize her chosen victims: Billy and Amanda. Ollie shoots Mrs. Carmody in the stomach with a revolver found in Amanda's purse, killing her, causing her congregation to break up. En route to David's car, Ollie in turn is bisected by the claw of a very large creature looking similar to a giant lobster or crab. David, Billy, Amanda, and an elderly, yet tough, school teacher Hilda Reppler reach the car and leave Bridgton, driving south for hours through a mist-shrouded, monster-filled New England. After finding refuge for the night, David listens to a radio, and through the overwhelming static possibly hears a single word broadcast, "Hartford". With that one shred of hope, he prepares to drive on into an uncertain future.