Anyway, the film. In short, two hitmen are stuck in a house somewhere in the back end of beyond while they wait for their target to come home. He's not due for a couple of hours, so they've got bugger all to do but talk. So they do. It's a risky move to take given that a lot of people appear to want something happening every couple of minutes in a film. However, it succeeds here given the interplay between the two men, their performances and the tension-inducing contrast between the lengthy dialogue pieces and the silence - silence that means you're focused on every tiny noise outside the house or every potential noise. Because, after all, there's nothing scarier than our imaginations.
Of course, being a horror film, not all goes to plan for the two characters especially when a third makes an appearance (and that third isn''t who you might expect). The whole thing works very well, and special mention has to go to the two leads whose relationship (jaded but focused older guy and a younger, nervous rookie) holds the film together, and who make you care about what happens to them. No easy job given their jobs and history.
If you're bored by obvious, unsubtle horror that leaves nothing to the imagination and you want to actually have to think about what you're watching, The Devil's Business is for you.