Paul Hibbard’s review published on Letterboxd:
Enough time has gone by that I feel comfortable calling this one of the great horror movies. At least in terms of 21st century horror, it and Let the Right One In are neck to neck as my favorite. This movie gets overshadowed a bit by its French Extreme cousin Martyrs, which is also a 5 star movie to me, but I prefer Inside. It's pretty easily on my top ten horror movies ever list.
The uniqueness of what it puts together in the plot really helps it stick out. A Christmas horror movie, from a country that isn't necessarily known for horror at the time (ironically the French extreme movement went away as fast as it came onto scene. According to the Martyrs director, partly because of the lack of support it received nationally). It's a female protagonist, female villain, fighting over a pregnancy, something that only a woman can have, obviously. And yet it's still one of the most extreme, merciless, brutal, take-no-prisoners films I've ever seen.
I read an essay once about how this film is a big allegory about France's racism and how it comments on a struggle to keep the French bloodline "pure" (ie white) and all of the undecurrent themes from the news channel about Muslims and the "suburban violence" talk throughout the movie and the muslim prisoner who is introduced later aren't just simple plotpoints, but real things the directors were saying. I don't know enough about French politics to pass those thoughts off as my own, but every time I'd hear a story in the subsequent years from France about riots, protests, conflict with muslims, and of course Je Suis Charlie, I would think back to this movie.