Nice and simple
I actually think this could have been very good. It's a simple story, nicely presented so that we come to understand how it could happen without having to believe in insane cults etc.
It's just too bad the beginning is so poorly executed. The whole first 45 minutes or so are so badly done, you have to really bear with it for the payoff.
More plausible characters/motivations would not be hard to come up with.
On the whole, I don't regret watching it, but it could have been so much better with just a little effort.