No subject should be off-limits for filmmakers willing to take a plunge. The degree of difficulty, however, tends to increase sharply with the weightiness of the premise. Dark Night takes an extremely provocative topic—a seemingly random mass shooting—and applies a heavy layer of arty artlessness to the material. Despite a number of striking images (Hélène Louvart’s camerawork is never less than severely beautiful), it rarely feels like it’s been thought through enough to really jell.