The morning after a violent thunderstorm, David Drayton (Thomas Jane) and his wife Stephanie (Kelly Collins Lintz) witness an unusual mist outside their lakeside home. Concerned with cleaning up in the aftermath of the storm, David, his neighbor Brent Norton (Andre Braugher), and David\'s eight-year-old son, Billy (Nathan Gamble), go to the local grocery store to buy supplies to fix the storm damage. Like the rest of the community, the store lost its power. With increasing police activity in the streets, Dan Miller (Jeffrey DeMunn) runs into the store with a bloody nose warning of something dangerous in the oncoming mist. After the mist covers the parking lot and they hear the scream of a man who ventures outside, the store patrons decide to seal themselves inside. The building is soon shaken by violent tremors, visibility reduces to nothing, and the customers grow more and more nervous about the fate of the screaming man; a siege mentality takes hold of them.