This is a "psychological" thriller as much or more than a horror film. First, Jim Sturgess is excellent and has a brilliant career ahead of him. Why we haven't seen more of Joseph Mawie, the "devil" character, over the years is beyond me. Mawie is extremely creepy and steals his scenes. Timothy Spall and Ed Marson are underrated, though you've seen them a thousand times.

The depiction of dark London is well done. And the supernatural elements are well introduced, conservatively used and blended well with the psychological travails of our main character. But there is so much going on that at times I caught myself trying to piece bits together to guess at what I was supposed to be guessing at. The "neighbor" functions as a good foil but we're led to believe he has/will have something to do with the plot, which he really doesn't. The "nephew" subplot, though of some importance to a a late plot explanation, becomes annoying early on and the actor is less than convincing.

Fun nonetheless. Difficult to make a passable horror film these days.