Halloween, on Oct. 31, is the annual celebration of ghosts, witches and all things scary. Its roots in northern Europe go all the way back to an ancient pagan festival on the day, it was believed, that the dead walked among the living. Today, "The Walking Dead" is a hit T.V. show about a world overrun by zombies. Zombies are everywhere in popular culture right now. VOA’s Steve Baragona looks at why the world is in the throes of a zombie invasion.