I've been wanting to see Martyrs
for ages. I can't remember when I first saw the trailer, but it has been on my list for years! While known for it's violence, I think the story, and how it unfolds are the real strengths of this film. It's a unique, chilling and well told story that only reveals its full plot at the very end. Well done!
There's also a US remake from 2015. Why anybody would want to bother with that is beyond me! See the original!