Look, you can't really review this kind of movie without a big spoiler alert.
So this is the big spoiler alert: I will reveal NOTHING of the plot...so nothing will be spoiled.
This IS what I can say: David Fincher is a brilliant director who took a script that started out as something exceptionally intriguing and pushed it through and made it as believable as he could, given the story.
It is worth it, to watch this thing, at first. By the end, you just want to go home and wail, WHY DIDN'T THEY FIGURE OUT WHAT THE FUCK THEY WERE DOING?! Oh, Lord Jesus, carry me off to the land of peace where I will no longer have to endure these types of misses ever again.
And now I will go back on my promise about the spoiler:
The butler did not do it. Because there is no butler. (But I've ruined nothing here, since there is never any talk of any butler.)
Slick stuff dishonestly drawn.
Come on, everyone. Try harder.