Watched this movie last night and thought it was good. I was more interested in what happens than them figuring out what it was because you figure it out long before they do. Spoiler in the comment.
spoiler
At some point I also thought it was all in their head because the clock seemed to be stuck at the same time. Now that I think about it, it also works if everything was in their head and they went sort of Amityville crazy. By the time the sheriff comes, everything is back to normal except for the things they themselves caused. The girl's eyes turned brown near the end, but it's back to cloudy again. I'm curious to see what the coroner's autopsy would have revealed. All the internal stuff that happened to him, or just the stab wound.
I wanted to really like it, and it was a good little movie, but it didn't quite 'wow' me. It wasn't bad by any means, and I liked that it was an original movie (instead of a sequel/reboot), but I guess it just didn't land with me quite right. Respect to the filmmakers though!