I don't want to say too much about the plot, because I honestly had no idea where the story was going. Even the final scenes had my complete attention because I could not predict what would happen next at any point. The film begins with a young girl, Lucie, escaping from captivity. She goes into a foster home of some kind and becomes close with another young girl there, Anna. We then join the two girls years later, as Lucie is trying to find her captors.
If you are just looking for a straight forward gore fest then Martyrs is possibly not for you. It gets pretty wanky and heady, but I think that the grim subject matter (which I can't really talk about without giving too much away) is explored excellently with this unique mix of "horror" and drama. The soundtrack is also amazing. Scenes that would normally be accompanied by scary or intense horror scores are given softer acoustic and piano music. The whole tone of the scene changes and becomes about something other than the sensationalism of violence. That being said, it's still a completely extreme film, in subject matter and visually, so perhaps horror fans are the only people who will be able to stomach it.
I really, really dug this film.