This movie is brutal, gory, and wonderful. Justine’s descent into madness, aided by her sister Alexia, is mesmerizing and wrenching. There are scenes of great beauty and warmth, and scenes of utter depravity, and the emotional whiplash is disorienting. The idea behind it is relatively simple, and could easily have been played for laughs, but it’s taken with utmost seriousness and devastating honesty.