I don't get the ending **** SPOILER ALERT! *****

If the wife was doing all the murders, then what the
heck happened towards the end ?. I mean they just
turned everything on it's head.

The writer/director can't get away this easily, by
just turning it upside down in the last 5 minutes.
There are so many loose ends that I don't even know
where to begin! Like those people who got bumped-off
when the hubby was out buying toothpaste, for instance.

It means the entire movie was a L-I-E.

That major plot-twist at the end there was overkill.
I understand the filmmaker's desire to use it as a
tool. It puts their movie into that category where
you walk out arguing with your spouse/friends about
what you've just collectively witnessed --but for it
to make sense, you at least have to leave some doubt
in the mind all along. The entire time you have the
wife killing them all and then quietly you pin every-
thing on somebody else.

Or did they both kill everybody ?.