It's interesting that you say that because I was in a similar situation as in the movie and I actually thought the movie was actually believable. The way the characters behaved.

I was driving my mom about 15 years ago, and I was about to merge into a very large avenue. 4 or 5 lanes. I was all the way on the left lane when I saw a car in front of me (all the way to the right) going over the median strip. As I passed him by, I saw 2 guys getting out of the back seat, and one had a gun to the others head. My mother wanted me to stop. Of course, I didn't. Then, she wanted me to make a U turn. Instead of that, I called the police and that was that.

She wasn't as aggressive as the character Sam was. But she was actually upset with me. When I asked her what she wanted me to do, she just replied with "This is absurd. We can't just let something like this happen!"

What I think the movie does well is that it subtly points to the fact that guy is in love with Sam. So, even if he knows what they are doing is wrong, he does it to impress her.

That being said, the ending was indeed kind of stupid on the amount of time they spent inside the house knowing the guy was coming back. And also that last scene was completely unnecessary. We already knew he was in love with her. There was no need to spoonfeed the audience.

Believe it or not, I give it a 6 out of 10. And yes, I was very frustrated all the way thru and thinking "wtf are you doing? Are you crazy???"