At 2 hours run-time you could be put off watching this when taking poor reviews into consideration and particularly if you expect the blindfolded concept to be an imaginatory stretch too far. However, with practical answers quickly offered up in the film as to the mechanics of apocalyptic survival without sight you can begin to suspend disbelief and settle into the plot development. Strong acting, and for that matter an incredible cast line-up, help it flow from a sluggish start to a rapid finish, like the river running through the film. Some critics pick up on the weak character development, but it's wrong to get too bogged down in irrelevant back stories that could just needlessly dilute the storyline. Bullock is a tour de force (as always) and certainly adds credibility to what could easily be a lame duck horror-thriller if acted out by unknown actors. The demons (or whatever spectre name they may be assigned) are, and remain, a largely unexplained mystery, along with a box of other miscellaneous loose threads. Nevertheless, the trick is to just go with the flow and not over-analyse what is overall a better than average B-movie.