Stephen King's novels are usualy hard to properly turn into movies as they are mostly about what's going on in character's heads - not this time. "The Mist" is not so much about monsters that wait outside but how people react when faced with fear and what they do to each other in panic. Her character starts as unimportant one,she is just a local spinster that nobody takes seriously but as the story progress,she really starts brainwashing everyone's heads with fear,religion and manipulation (King's favourite theme) - Marcia Gay Harden gives one of the best performances that I saw recenty and is easily one of my favourite baddies.
I don't remember when I hated some movie character so passionately the last time around,could easily throw her out in the mist myself if only I was there.
Excellent actress.