This will sound harsh but "Greystone Park" (or "The Asylum Tapes" if you're outside the US) is comfortably among the worst movies I have ever seen.
No real plot, no thrills, no frights, no nothing.
Bad acting (I mean really, really bad), bad sound, bad camera work and even worse editing. I fully appreciate that the film is supposed to be a "found tapes" film - but that is no excuse to produce a 90+ minute film of which most of it you can't actually see what's going on. Adding loud bangs to the footage you can't see doesn't scare anybody above the age of four - not in the year 2012 anyway.
Sean Stone's father Oliver is a talented movie maker and one of the more important directors of the 20th century. This piece of garbage might be Stone Jr's first, last and only contribution to the annals of cinematic history.