Achtung! The idea behind this German Experiment is nothing new. In fact, nearly everything in this intense psychological drama stems from Philip Zimbardo's landmark Stanford Prison Experiment, wherein men were randomly assigned roles as prisoners or guards. Of course, we all know how this drama plays out: the prisoners band together while the guards tend toward fascism.
Still, Oliver Hirschbiegel's film (which cites Mario Giordano's novel Black Box as its inspiration) is a taut, well-realized exploration of the fine line separating man from beast. But what makes this movie work is the severity of the violence and the quality of the acting--especially the contrast and conflict between the dark-haired hero (a prisoner played by Moritz Bleibtreu) and his sadistic nemesis (a guard portrayed to perfection by Justus von Dohnanyi). Disturbingly successful.