I get the ending, but it's weak. (SPOILERS)
Okay, so the father, for all his supposed fearlessness, is helpless in the face of these events. Even his wife has more gumption, and we see the failure of his religion to deal with the real evils of the world. Truly, he is revealed as a craven figure, who allows a man to take his daughter to presumably rape and murder without even a scuffle. It's a condemnation of the easy, religious life or at least an attempt to expose it as weak.
But unless we know the story behind this movie (which I don't, other than in the vaguest terms), we are left not knowing what is to happen. So we can't grasp the full significance of events. Why is Roberts so upset? You are expected to know that he will kill these people, but if you didn't read about the case before viewing, you don't know that.
It all ends so abruptly and without development that it's confusing. Meanwhile huge amounts of time are devoted to 'atmosphere' and watching the characters' slow progress toward the scene of their eventual crime. Something went seriously wrong here.
"Now let's have an intelligent conversation. I'll talk and you listen."