Alex Gibney finds the ideal outlet for his perennial style of sober, steady doom-mongering, in a story about something that may legitimately yield nothing less than doom itself. International governmental conspiracies! Covert technological war! Nuclear annihilation! It's all very abstract and absurd-sounding when examined objectively, but the essential point of Zero Days is to discourage such an analysis - covert or not, this stuff is the stuff of our daily lives, and ignorance is no excuse. With typical extreme subjectivity, and equally typical thoroughness, Gibney outlines enough detail to make a placated public quake, if only for the length of this documentary's running time. Whatever your take on the real-world seriousness of this suspiciously secretive subject - the Stuxnet virus - its specific seriousness in this context is virtually inarguable, and thus a most arresting synergy is created between topic and treatment. Gibney is as didactic as usual, and thankfully so; if he's perhaps too blunt at times, one might attribute this to personal interpretation, and appreciate that Zero Days has an obligation to total clarity for the whole of its audience. That audience would be wise to pay attention, however, and here is where the film slacks in its obligations: it doesn't afford its viewers any such slack room, and its density is a potential drawback. But its urgency is palpable, and perfectly communicated via an attention to detail that is surely remarkable given the difficulty Gibney evidently had in obtaining the information he required.