Not a good'un.
'A Patch of Fog' isn't bad per se, I just can't really tell you anything that I particularly enjoyed about it. Sure I like Stephen Graham and Conleth Hill, though I've seen better from both. The plot does have a few moments of goodness with solid twists and a neat end, though those are few and far between as they are surrounded by much mediocre-ness.
Graham and Hill do make sure it remains mildly watchable, though everything else kinda hinders more than it helps the film. Despite a 90 minute run time, it makes for a slow watch - not helped by the fact that the filmmakers let the cat out the bag, so to speak, very early on, a bit more suspense/subtlety would've went a long way.