Subtlety is probably too much to expect from Marc Forster's World War Z. This is massive-scale 3D filmmaking, and in that context, some of it works like gangbusters. The world is destroyed by a virus that turns people into zombies. Within 12 seconds of being bitten by an infected host, any human becomes a twisted, soulless creature with cloudy, heroin-addict eyes, motivated only by a ravenous need to tear into healthy flesh. Brad Pitt plays a New York City family man who strives to protect his kids from these fearsome drones, at first by sticking close but later by leaving. The best way to save them, he realizes, is to serve the greater good and find the source of the killer virus. It's all pretty noble, and if nothing else, World War Z shows off some horrifically effective filmmaking: An early sequence, in which Pitt's Gerry figures out something has gone terribly wrong as he's driving his wife (Mireille Enos) and two generically adorable daughters in Manhattan, is that rare evocation of chaos that isn’t chaotic itself. The picture tangles with some potentially fascinating geopolitical ideas but doesn't know what to do with them. It does make good use of Pitt, who has in the years since his reign as Sexiest Man Alive turned casualness into a discernible, potent style. In World War Z, he's a deeply comforting presence, the dad who promises to take care of everything--everything!-- and actually manages to do so.