If you rent or buy "World War Z" chances are good you're going to pause it at some point.

Oh, sure, it's long. But it's also all over the place, suggesting several films that didn't quite jell.

Largely that's because director Marc Forster doesn't know what he wants -- a heartbreaking drama like "28 Days Later" or a thriller like "Argo." The action, as a result, shifts so rapidly it's hard to decide which emotion to conjure.

Brad Pitt plays the perfect dad -- a pancake-making rock who wants no part of the plague that's sweeping the world. The president has died, major cities are in chaos and zombies are roaming the streets.

In the first hour or so Pitt and family race around the country trying to get to a safe zone -- a ship in the Atlantic. Forster keeps the action pitched and makes Pitt like Tom Cruise in "War of the Worlds."

Then the hero -- a high-level United Nations expert -- hears the call of duty and the film shifts into an intellectual thriller where scientists hypothesize about cause and effect.

"Mother Nature is a serial killer," one brain tells him. "She can't fight the urge to get caught." So, with a "Zero Dark Thirty" SEAL team, Pitt goes into the belly of the beast and tries to discern where it started and how it can be stopped.

This involves plenty of travel (to Jerusalem, no less, where a wall keeps the zombies at bay) and more running. He picks up a partner, too, and she becomes his best ally in the war.

Before "World War Z" settles into an easy resolution, it experiences an "Argo" moment that quickly becomes "Snakes on a Plane."