From NetFlix:

Newlyweds Cliff (Steve Zahn) and Cydney (Milla Jovovich) are enjoying a perfect honeymoon in Hawaii — until they run into a pair of menacing hikers, Nick (Timothy Olyphant) and Gina (Kiele Sanchez). As it turns out, the two are dangerous killers who begin stalking the not-so-happy couple. David Twohy wrote and directed this action-packed thriller, which co-stars Marley Shelton, Katie Chonacas and Chris Hemsworth.

Give this film only a B. The acting was just fine. I have never seen Steve Zahn do a bad job or appear in a movie that I did not want to watch. HOWEVER … you have to suspend disbelief in certain parts. Although there is a wonderful plot twist, I had great difficulty understanding the details. Perhaps I was just too tired to grasp the details. Try watching the film without help. After that you can read wikipedia which explains everything. There are just a few body wounds, nothing more unsettling than that. The very last few seconds are a clever conclusion.