Amanda is a married third grade teacher. While her husband is away on a business trip to New York, she goes to the grocery store. Her husband gave her a pistol to protect herself while he is gone. A mysterious mist engulfs the town, trapping people inside the grocery store. Amanda bonds with David Drayton and his son Billy during their time in the store. On the third day of the crisis, Amanda, David, Billy and other survivors decide to leave. They are stopped by the religious Mrs. Carmody, who attempts to sacrifice Amanda and Billy. However, Mrs. Carmody is killed and they are able to leave the store.
Once outside in the mist, Amanda and the others drive around in David's vehicle until it runs out of gas. Amanda, Irene and Dan decide to kill themselves, and David decides to kill Billy along with them, as there are just enough bullets for those four and not himself. Amanda holds Billy in her lap while he is sleeping, and David turns the gun on her and his son. Amanda, Billy, Irene and Dan are all killed. David steps outside the vehicle to see that the army has arrived and the mist is clearing away.