Stephen King wrote his novella The Mist in 1980, the same year that John Carpenter released The Fog.
It's a classic King formula, too classic really. A bunch of clashing small town characters find themselves enclosed in a glass-fronted supermarket after a strange mist (rather dense and fog-like it has to be said) containing nasties from another dimension drifts in off the local lake.
Frank Darabont has been successful with his King adaptations before (The Green Mile, The Shawshank Redemption) but there's something rather clunky about this movie. It seems determined to hide its own hackneyed soul within a screenwriter's miasma, but few of Darabont's strategems in this respect ring true and a lot of them ring dumb — including what has been described as the "Cormac McCarthy-style" ending, which appears to have been enforced in spite of the fact that it runs against the logic of the characters and their situation. Uncompromising yes, but also unnecessary. (Dr Kermode is wont to say that movies like Slumdog Millionaire have earned their upbeat endings; well, this is one that simply hasn't done enough to earn its downbeat conclusion. And tanks, gas-masks and flame throwers? Puhlease....)
Marcia Gay Harden's religious nut Mrs Carmody comes off at first as a bit of a joke, but does in fact become unnervingly scary as time passes. But her assumption of power within this trapped community plagued by periodic attacks by Doctor Who-style CGI beasties, isn't as convincing as it might have been, because the script is low on psychological insight and manages the human interactions so unrealistically — when one group of people are talking it is assumed that everyone else inside the shop is silent. (Even Lost handles its background extras less absurdly.)
And the monsters outside seem strangely unwilling to keep up a consistently imminent level of threat, which is yet another reason why the desperate decision taken at the end already seems precipitous, even before the director's final reveal.