After a violent storm in a community in Maine, the local artist Dave Drayton drives from his lake-side house with his son Billy and his arrogant neighbor, lawyer Brent Norton, to the supermarket to get supplies. On the way, they see a heavy mist, and later, see military convoys, police, fire trucks, and ambulances heading into it. In the supermarket, a frantic local arrives crying that there is something alive in the mist. The manager closes the front entrance but the store is enclosed by the mist. David, another client and two employees go to the back of the store to start the backup generator. When they open the back entrance, Norm the cashier (Chris Owen) is seized and dragged away by fierce tentacles. David and two survivors succeed in closing the loading door. When they tell the rest of the people in the store what happened, Brent does not trust his own perception, believing it is a prank. The God-fearing Mrs. Carmody preaches the Apocalypse and says that she is the agent of the Lord on Earth. Soon the group discovers that they are under siege by blood-thirsty creatures from another dimension that have reached our planet through a window opened by a failed military research project. The crazy Mrs. Carmody has many followers and starts to make dangerous speeches. Absent any alternatives, a small group led by David decides to take a chance, leave the supermarket, and get to his car, hoping to escape the mist.