After a violent storm hits a small Maine town, David Drayton, his young son Billy, and several neighbors go to a local supermarket to gather supplies. Suddenly, a thick, unnatural mist rolls in, trapping them inside. As panic spreads, it becomes clear that something deadly lurks within the mist—monstrous creatures that attack anyone who ventures outside.

Inside the store, fear turns people against each other. A religious zealot, Mrs. Carmody, gains followers by claiming the mist is divine punishment. As her influence grows, she incites others to sacrifice people to appease God's wrath.

David and a small group plan to escape, fearing the humans inside may become more dangerous than the monsters outside. They make a run for his car and drive until they run out of gas. With no help in sight and the mist closing in, David makes a devastating decision to spare the others from being killed by the monsters.

Just moments later, the military arrives, clearing the mist and rescuing survivors—revealing that help was moments away, making David's decision tragically pointless and heartbreaking.