[Hotfire]

I think the title was "In The Beginning".
The gist of the plot is a mother and daughter are being constantly assaulted while sleeping. They wake each time tied up, gagged and blindfolded. The rapist then abuses and rapes them both. This continues to happen as they move from city to city to get away.

Finally, a detective investigating the case discovers it's the son who is doing it and instead of arresting him, he joins him and then they do the same to his family.

Thanks in advance,
~hf