Enjoyed it up until the last section, about 10 minutes before the end (or there-abouts) where, predictably, the lady in the wheelchair is found by the policeman with knife in hand and, of course is assumed to be the cause of the deaths around the place. The 'doll' of course, is not considered a suspect, since dolls don't usually attack people with knives. Could see that coming, as I'd guess most people would also, which took from the previous successfully unpredictable tensions that the movie possessed.
Hence, I think it would only warrant around 3 out of 5, unfortunately,
B.R.